CN112235577B

CN112235577B - Prediction method and device of chrominance block

Info

Publication number: CN112235577B
Application number: CN202010772909.4A
Authority: CN
Inventors: 马祥; 陈建乐; 杨海涛
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-12-13
Filing date: 2018-12-13
Publication date: 2021-08-20
Anticipated expiration: 2038-12-13
Also published as: CN112235577A; CN116781915A; EP3883245A4; US20210314581A1; EP3883245A1; CN117319670A; CN111327903B; CN117082250A; WO2020119449A1; US11595669B2; US20230156202A1; CN111327903A; BR112021011427A2

Abstract

The application provides a prediction method and a prediction device of a chrominance block, and belongs to the technical field of videos. The method comprises the following steps: obtaining a maximum brightness value and a minimum brightness value in brightness pixels corresponding to pixels adjacent to a target chromaticity block, obtaining a first chromaticity value corresponding to the maximum brightness value and a second chromaticity value corresponding to the minimum brightness value, then calculating a first difference value between the maximum brightness value and the minimum brightness value, if the first difference value is larger than 0, performing right shift processing on the first difference value according to the number of valid bits of the first difference value and a first preset bit depth bit-depth to obtain a second difference value, then determining an intra-frame prediction model parameter corresponding to the target chromaticity block according to the first chromaticity value, the second chromaticity value and the second difference value, and determining prediction information of the target chromaticity block according to the intra-frame prediction model parameter and brightness reconstruction information corresponding to the target chromaticity block. By the method and the device, the prediction efficiency of the chroma block can be improved.

Description

Prediction method and device of chrominance block

The application is a division of a Chinese patent application with the application number of 201811527100.4 and the application name of 'prediction method and device of chromaticity blocks' filed by the intellectual property office of China on 12, 13 and 2018.

Technical Field

The present application relates to the field of video technologies, and in particular, to a method and an apparatus for predicting a chroma block.

Background

With the development of internet technology, video applications are increasing, and the demand for high-definition videos in the video applications is increasing, however, because the data volume of the high-definition videos is large, if the high-definition videos are required to be transmitted in a limited network bandwidth, the high-definition videos need to be encoded. The general encoding process mainly includes intra-frame prediction, inter-frame prediction, transformation, quantization, entropy coding, in-loop filtering and other links.

In the related art, when performing intra prediction, for any chroma block, a cross-component linear mode (CCLM), which may also be referred to as a cross-component prediction mode (CCP), which may also be referred to as a (cross-component intra prediction, CCIP), may be used to determine prediction information, which is a chroma intra prediction method using correlation between luma and chroma, and it uses a reconstructed luma component to derive current chroma block prediction information according to a linear model, which may be expressed as the following equation: pred_C(i,j)＝α*recⁱ _L(i, j) + β, α and β are intra prediction model parameters, α is the scaling factor, β is the offset factor, pred_C(i, j) is the predicted value of the chroma pixel at the (i, j) position, recⁱ _LAnd (i, j) the luminance reconstruction pixel value at the position (i, j) after the luminance reconstruction block corresponding to the current chrominance block is down-sampled to the resolution of the chrominance component. The scaling coefficients and offset factors do not need to be transmitted encoded, but are derived using edge pixels of neighboring reconstructed blocks of the current chroma block and luma pixels at corresponding positions of the edge pixels.

Thus, each chroma block using the CCLM needs to determine the intra prediction model parameter, but the complexity of determining the intra prediction model parameter in the related art is high, resulting in low prediction efficiency of the chroma block.

Disclosure of Invention

In order to solve the problems of the related art, embodiments of the present application provide a method and an apparatus for predicting a chroma block. The technical scheme is as follows:

in a first aspect, a method for predicting a chroma block is provided, where the method includes:

the method comprises the steps of obtaining a maximum brightness value and a minimum brightness value in brightness pixels corresponding to pixels adjacent to a target chromaticity block, and obtaining a first chromaticity value corresponding to the maximum brightness value and a second chromaticity value corresponding to the minimum brightness value. And if the first difference value between the maximum brightness value and the minimum brightness value is larger than 0, performing right shift processing on the first difference value according to the number of effective bits of the first difference value and a first preset bit depth bit-depth to obtain a second difference value. And determining intra-frame prediction model parameters corresponding to the target chrominance block according to the first chrominance value, the second chrominance value and the second difference value. And determining the prediction information of the target chroma block according to the intra-frame prediction model parameters and the brightness reconstruction information corresponding to the target chroma block.

According to the scheme shown in the embodiment of the application, when the current chrominance block (which may be referred to as a target chrominance block) is determined, the encoding mode of the target chrominance block may be determined, and if the encoding mode is CCLM, pixels adjacent to the target chrominance block may be determined, and then the maximum luminance value and the minimum luminance value of luminance pixels corresponding to the pixels may be determined. And a chrominance value corresponding to the maximum luminance value (i.e., a first chrominance value) and a chrominance value corresponding to the minimum luminance value (i.e., a second chrominance value) may be determined. The difference between the maximum luminance value and the minimum luminance value, i.e. the first difference value, may then be determined. And then judging whether the first difference is larger than 0, if so, determining the number of effective bits of the first difference, and performing right shift processing on the first difference by using the number of the first effective bits and a first preset bit-depth to obtain a second difference.

Then, the intra prediction model parameter corresponding to the target chroma block can be determined by using the first chroma value, the second chroma value and the second difference value. The intra prediction model parameters include a scaling factor (which may also be referred to as a target scaling factor) and an offset factor (which may also be referred to as a target offset factor). And obtaining brightness reconstruction information corresponding to the target chroma block, and then determining the prediction information of the target chroma block by using the determined intra-frame prediction model parameters and the brightness reconstruction information corresponding to the target chroma block.

In this way, when the scaling coefficient is determined, the right shift processing is performed on the first difference between the maximum luminance value and the minimum luminance value according to the number of significant bits of the first difference and the first preset bit-depth, so that the calculation amount for determining the scaling coefficient can be reduced, and further, the calculation amount for determining the offset factor can be reduced, thereby reducing the calculation complexity of the intra-frame prediction model parameters and improving the prediction efficiency of the chrominance block.

In a possible implementation, a third difference between the number of significant bits of the first difference and the first preset bit-depth is determined. And if the third difference is larger than 0, performing right shift processing on the first difference according to the third difference to obtain a second difference.

According to the scheme shown in the embodiment of the application, the difference value between the maximum brightness value and the minimum brightness value can be determined and can be represented as a first difference value, then whether the first difference value is larger than 0 or not can be judged, if the first difference value is larger than 0, the number of the effective bits of the first difference value can be determined, and a first preset bit-depth which is stored in advance can be obtained. Then, the difference between the number of significant bits of the first difference and the first preset bit-depth is determined, which may be determined as a third difference.

Then, whether the third difference is greater than 0 may be determined, and if the third difference is greater than 0, the first difference may be right-shifted according to the third difference to obtain a second difference.

Therefore, the first difference value is not directly subjected to right shift by the first preset bit-depth bit, but the difference value between the first difference value and the first preset bit-depth is taken as the right shift digit, so that the effective bit of the first difference value can be reserved as far as possible, and the coding and decoding performance is better.

In a possible implementation manner, the first difference is shifted to the right by the third difference bit to obtain the second difference.

In a possible implementation manner, the intra prediction model parameter corresponding to the target chroma block is determined according to the first chroma value, the second chroma value, a preset value of a normalized shift parameter, the second difference value, and the minimum luminance value.

Wherein the normalized shift parameter is used for shift processing, and a preset value of the normalized shift parameter may be preset and stored in the apparatus mentioned below.

In the scheme shown in the embodiment of the present application, each chroma block using the CCLM corresponds to an intra prediction model parameter, and the intra prediction model parameter includes an offset factor and a scaling factor. The scaling factor and the offset factor corresponding to the target chromaticity block can be determined according to the first chromaticity value, the second chromaticity value, the preset value of the normalized shift parameter, the second difference value, the minimum brightness value and a preset formula.

In a possible implementation manner, a scaling factor in an intra prediction model parameter corresponding to the target chroma block is determined according to the first chroma value, the second difference value, and the preset value. And determining an offset factor in an intra-frame prediction model parameter corresponding to the target chroma block according to the scaling coefficient, the second chroma value, a target value of a normalized shift parameter and the minimum brightness value, wherein the target value of the normalized shift parameter is determined according to the preset value of the normalized shift parameter and the third difference value.

According to the scheme shown in the embodiment of the application, the preset value of the normalized shift parameter can be obtained, and the preset value is a preset parameter value aiming at the normalized shift parameter. The preset value of the normalized shift parameter may then be added to the second difference to obtain a target value of the normalized shift parameter. Then, the first chrominance value, the second chrominance value, the preset value of the normalized shift parameter and the second difference value can be used to be input into a preset formula to obtain a scaling coefficient corresponding to the target chrominance block, and then the scaling coefficient, the target value of the normalized shift parameter and the minimum luminance value are input into another preset formula to obtain an offset factor corresponding to the target chrominance block. In addition, if the second difference is less than or equal to 0, the target value of the normalized shift parameter is a preset value of the normalized shift parameter, and the preset value of the normalized shift parameter may be subsequently used to determine the prediction information. In this way, the determined intra prediction parameters can be made more accurate due to the use of the target values for the normalized shift parameters.

In one possible implementation form of the method,

wherein a is the scaling coefficient, diff is the second difference, maxC is the first chroma value, minC is the second chroma value, and N is the preset value.

The scheme shown in the embodiment of the application uses a formula

The scaling factor is determined, and since the diff is right-shifted with respect to the first difference, it can be determined in a look-up table

The complexity is reduced.

In one possible implementation form of the method,

wherein the content of the first and second substances,

a is the scaling coefficient, diff is the second difference, maxC is the first chroma value, minC is the second chroma value, and N is the preset value.

The scheme shown in the embodiment of the application uses a formula

The complexity is reduced.

In a possible implementation manner, an initial scaling factor in an intra prediction model parameter corresponding to the target chroma block is determined according to the first chroma value, the second chroma value, the preset value, and the second difference value. And if the fourth difference between the number of the effective bits of the initial scaling coefficient and the second preset bit-depth is greater than 0, performing right shift processing on the initial scaling coefficient according to the fourth difference to obtain the scaling coefficient in the intra-frame prediction model parameter corresponding to the target chroma block.

In the scheme shown in the embodiment of the present application, the initial scaling factor in the intra prediction model parameter corresponding to the target chroma block may be determined by using the first chroma value, the second chroma value, the preset value, and the second difference, and the process may refer to the above-mentioned mode one or mode two. Then, a second preset bit-depth preset corresponding to the scaling coefficient can be obtained, then, a fourth difference value between the number of the significant bits of the initial scaling coefficient and the second preset bit-depth is determined, whether the fourth difference value is greater than 0 or not is judged, if the fourth difference value is greater than 0, right shift processing can be performed on the initial scaling coefficient according to the fourth difference value, and the scaling coefficient corresponding to the target chrominance block is obtained.

Thus, after the initial scaling coefficient is shifted, the bit-depth of the scaling coefficient is reduced, so that the complexity of multiplication in the subsequent determination of the prediction information can be reduced.

In a possible implementation manner, the initial scaling factor is shifted to the right by the fourth difference bit, so as to obtain a scaling factor in an intra prediction model parameter corresponding to the target chroma block.

In one possible implementation, the method further includes: and if the fourth difference is larger than 0, determining the difference between the sum of the preset value of the normalized shift parameter and the third difference and the fourth difference as the target value of the normalized shift parameter.

In the solution shown in the embodiment of the present application, if the fourth difference is greater than 0, a difference between a sum of the preset value of the normalized shift parameter and the third difference and the fourth difference may be determined as a target value of the normalized shift parameter.

In a possible implementation manner, the second preset bit-depth is a bit-depth of the intra interpolation filter coefficient.

In the scheme shown in the embodiment of the application, the second preset bit-depth is set as the bit-depth of the intra interpolation filter coefficient, and the complexity of intra prediction can be aligned.

In a possible implementation manner, the determining, according to the scaling factor, the second chrominance value, the target value, and the minimum luminance value, an offset factor in an intra prediction model parameter corresponding to the target chrominance block includes:

b minC- ((a minY) > k), where b is the offset factor, a is the scaling factor, minC is the second chrominance value, minY is the minimum luminance value, and k is the target value.

In the solution shown in this embodiment of the application, a preset offset factor calculation formula may be obtained, that is, b is minC- ((a minY) > k), which indicates that a difference is obtained between values of minC and a minY after being shifted by k bits to the right, so as to obtain an offset factor b corresponding to the target chrominance block, and the scaling coefficient a, the second chrominance minC, the target value k of the normalized shift parameter, and the minimum luminance value minY may be substituted into the formula, so as to determine the offset factor b corresponding to the target chrominance block, where k is N + shiftLuma, and shiftLuma is the aforementioned third difference.

In one possible implementation, the method further includes: and if the first difference value is not larger than 0, determining that the scaling coefficient in the intra-frame prediction model parameter is 0, and determining that the offset factor in the intra-frame prediction model parameter is the second chrominance value.

In the solution shown in the embodiment of the present application, if the first difference is not greater than 0, it may be determined that the scaling factor is 0, and then, using a formula b ═ minC- ((a × minY) > k), the second chromaticity value, the target value of the normalized shift parameter, and the minimum luminance value are substituted into the formula, so that b ═ minC may be obtained, that is, the offset factor is the second chromaticity value. In this way, it may be determined that the intra prediction model parameter corresponds to the target chroma block when the first difference is not greater than 0.

In a possible implementation manner, the preset value of the normalized shift parameter is a bit-depth of the first difference, or a bit-depth of a luminance pixel, or a sum of the bit-depth of the first difference and a second preset value, or a product of the bit-depth of the first difference and a third preset value, or a bit-depth of one byte.

The second preset value is a positive integer, such as 4 bits, and the third preset value is a positive integer, such as 2 bits.

In the solution shown in the embodiment of the present application, the preset value of the normalized shift parameter may be set to be bit-depth of the first difference. The preset value of the normalized shift parameter may also be set to the bit-depth of the luminance pixel.

The preset value of the normalized shift parameter may also be set as the sum of the bit-depth of the first difference and a second preset value, for example, the bit-depth of the first difference is 4 bits, the second preset value is 4 bits, and the preset value of the normalized shift parameter may be 8 bits.

The preset value of the normalized shift parameter may also be set as the product of the bit-depth of the first difference and a third preset value, for example, the bit-depth of the first difference is 4 bits, the third preset value is 2, and the preset value of the normalized shift parameter is 8 bits.

The preset value of the normalized shift parameter may be set to a bit-depth of one byte.

Thus, since the preset values of the normalized shift parameters can be adjusted to be any one of the above values, which are all smaller than 16 in the related art, bit-depth of the numerical values in the table can be reduced during subsequent table look-up, so that the data volume of the table can be reduced.

In a possible implementation, the first preset bit-depth is smaller than the bit-depth of the luminance pixel.

In a second aspect, a prediction apparatus for a chroma block is provided, where the prediction apparatus includes a processor and a memory, where the memory is used to store instructions executable by the processor, and the processor implements the prediction method for the chroma block provided in the first aspect by executing the instructions.

In a third aspect, an apparatus for predicting a chroma block is provided, where the apparatus includes one or more modules configured to implement the method for predicting a chroma block provided in the first aspect.

In a fourth aspect, a computer-readable storage medium is provided, which stores instructions that, when executed on a computing device, cause the computing device to perform the prediction method for chroma blocks provided in the first aspect.

In a fifth aspect, there is provided a computer program product comprising instructions which, when run on a computing device, cause the computing device to perform the method for prediction of chroma blocks as provided in the first aspect above.

The beneficial effects brought by the technical scheme provided by the embodiment of the application at least comprise:

in the embodiment of the present application, when determining the prediction information of the target chrominance block, the apparatus may obtain a maximum luminance value and a minimum luminance value of luminance pixels corresponding to pixels adjacent to the target chrominance block, obtain a first chrominance value corresponding to the maximum luminance value and a second chrominance value corresponding to the minimum luminance value, and then determine a first difference between the maximum luminance value and the minimum luminance value. If the first difference is greater than 0, right shift processing can be performed on the first difference according to the number of valid bits of the first difference and a first preset bit-depth to obtain a second difference. And then determining intra-frame prediction model parameters corresponding to the target chroma block according to the first chroma value, the second chroma value and the second difference value, and then determining prediction information of the target chroma block according to the intra-frame prediction model parameters and the brightness reconstruction information corresponding to the target chroma block. In this way, when the intra-frame prediction model parameter is determined, the right shift processing is performed on the first difference value between the maximum brightness value and the minimum brightness value according to the number of significant bits of the first difference value and the first preset bit-depth, so that the calculation amount of the intra-frame prediction model parameter can be reduced, and the prediction efficiency of the chroma block can be improved.

Drawings

FIG. 1 shows a block diagram of an example of a video encoding system for implementing embodiments of the present application;

FIG. 2 shows a block diagram of an example of a video encoding system including either or both of encoder 20 of FIG. 3 and decoder 30 of FIG. 4;

FIG. 3 shows a block diagram of an example structure of a video encoder for implementing embodiments of the present application;

FIG. 4 shows a block diagram of an example structure of a video decoder for implementing embodiments of the present application;

FIG. 5 depicts a block diagram of an example encoding device or decoding device;

FIG. 6 shows a block diagram of another example encoding device or decoding device;

fig. 7 shows an example YUV format sampling grid;

FIG. 8 illustrates one embodiment of a Cross Component Prediction (CCP) mode;

FIG. 9 shows a schematic view of an upper and left template;

FIG. 10 shows another schematic view of an upper and left template;

fig. 11 shows a flow diagram of a prediction method of a chroma block;

fig. 12 shows a flow diagram of a prediction method of a chroma block;

fig. 13 is a schematic diagram showing a structure of a prediction apparatus for a chroma block.

Detailed Description

To make the objects, technical solutions and advantages of the present application more clear, embodiments of the present application will be described in further detail below with reference to the accompanying drawings.

To facilitate an understanding of the present application, the system architecture referred to in the present application, and the concepts of the terms referred to, are first described below.

Video coding generally refers to processing a sequence of pictures that form a video or video sequence. In the field of video coding, the terms "picture", "frame" or "image" may be used as synonyms. Video encoding as used in this application (or this disclosure) refers to video encoding or video decoding. Video encoding is performed on the source side, typically including processing (e.g., by compressing) the original video picture to reduce the amount of data required to represent the video picture for more efficient storage and/or transmission. Video decoding is performed at the destination side, typically involving inverse processing with respect to the encoder, to reconstruct the video pictures. Embodiments are directed to video picture "encoding" to be understood as referring to "encoding" or "decoding" of a video sequence. The combination of the encoding portion and the decoding portion is also called codec (encoding and decoding, or simply encoding).

Each picture of a video sequence is typically partitioned into non-overlapping sets of blocks, typically encoded at the block level. In other words, the encoder side typically processes, i.e., encodes, video at the block (also referred to as image block, or video block) level, e.g., generates a prediction block by spatial (intra-picture) prediction and temporal (inter-picture) prediction, subtracts the prediction block from the current block (the currently processed or to be processed block) to obtain a residual block, transforms the residual block and quantizes the residual block in the transform domain to reduce the amount of data to be transmitted (compressed), while the decoder side applies the inverse processing portion relative to the encoder to the encoded or compressed block to reconstruct the current block for representation. In addition, the encoder replicates the decoder processing loop such that the encoder and decoder generate the same prediction (e.g., intra-prediction and inter-prediction) and/or reconstruction for processing, i.e., encoding, subsequent blocks.

The term "block" may be a portion of a picture or frame. The present application defines key terms as follows:

the current block: refers to the block currently being processed. For example, in encoding, refers to the block currently being encoded; in decoding, refers to the block currently being decoded. If the currently processed block is a chroma component block, it is referred to as a current chroma block. The luminance block corresponding to the current chrominance block may be referred to as a current luminance block.

Reference block: refers to a block that provides a reference signal for the current block. During the search process, multiple reference blocks may be traversed to find the best reference block.

Predicting a block: the block that provides prediction for the current block is called a prediction block. For example, after traversing multiple reference blocks, a best reference block is found that will provide prediction for the current block, which is called a prediction block.

Image block signals: pixel values or sampling signals within the image block.

Prediction signal: the pixel values or sample values or sampled signals within a prediction block are referred to as prediction signals.

Embodiments of the encoder 20, decoder 30 and encoding system 10 are described below based on fig. 1, 2 to 4.

Fig. 1 is a conceptual or schematic block diagram depicting an exemplary encoding system 10, such as a video encoding system 10 that may utilize the techniques of the present application (this disclosure). Encoder 20 (e.g., video encoder 20) and decoder 30 (e.g., video decoder 30) of video encoding system 10 represent examples of equipment that may be used to perform intra prediction according to various examples described in this application. As shown in fig. 1, encoding system 10 includes a source device 12 for providing encoded data 13, e.g., encoded pictures 13, to a destination device 14 that decodes encoded data 13, for example.

Source device 12 includes an encoder 20 and, in a further alternative, may include a picture source 16, a pre-processing unit 18, such as picture pre-processing unit 18, and a communication interface or unit 22.

The picture source 16 may include or may be any type of picture capture device for capturing real-world pictures, for example, and/or any type of picture or comment generation device (for screen content encoding, some text on the screen is also considered part of the picture or image to be encoded), for example, a computer graphics processor for generating computer animated pictures, or any type of device for obtaining and/or providing real-world pictures, computer animated pictures (e.g., screen content, Virtual Reality (VR) pictures), and/or any combination thereof (e.g., Augmented Reality (AR) pictures).

A picture can be seen as a two-dimensional array or matrix of sample points having intensity values. The sample points in the array may also be referred to as pixels (short for pixels) or pels (pels). The number of sampling points of the array or picture in the horizontal and vertical directions (or axes) defines the size and/or resolution of the picture. To represent color, three color components are typically employed, i.e., a picture may be represented as or contain three sample arrays. In the RBG format or color space, a picture includes corresponding red, green, and blue sampling arrays. However, in video coding, each pixel is typically represented in a luminance/chrominance format or color space, e.g., YCbCr, comprising a luminance component (sometimes also indicated by L) indicated by Y and two chrominance components indicated by Cb and Cr. The luminance (luma) component Y represents the luminance or gray level intensity (e.g. both are the same in a gray scale picture), while the two chrominance (chroma) components Cb and Cr represent the chrominance or color information components. Accordingly, a picture in YCbCr format includes a luminance sample array of luminance sample values (Y), and two chrominance sample arrays of chrominance values (Cb and Cr). Pictures in RGB format may be converted or transformed into YCbCr format and vice versa, a process also known as color transformation or conversion. If the picture is black, the picture may include only the luminance sample array.

Picture source 16 (e.g., video source 16) may be, for example, a camera for capturing pictures, a memory, such as a picture store, any type of (internal or external) interface that includes or stores previously captured or generated pictures, and/or obtains or receives pictures. The camera may be, for example, an integrated camera local or integrated in the source device, and the memory may be an integrated memory local or integrated in the source device, for example. The interface may be, for example, an external interface that receives pictures from an external video source, for example, an external picture capturing device such as a camera, an external memory, or an external picture generating device, for example, an external computer graphics processor, computer, or server. The interface may be any kind of interface according to any proprietary or standardized interface protocol, e.g. a wired or wireless interface, an optical interface. The interface for obtaining picture data 17 may be the same interface as communication interface 22 or part of communication interface 22.

Unlike pre-processing unit 18 and the processing performed by pre-processing unit 18, picture or picture data 17 (e.g., video data 16) may also be referred to as raw picture or raw picture data 17.

Pre-processing unit 18 is configured to receive (raw) picture data 17 and perform pre-processing on picture data 17 to obtain a pre-processed picture 19 or pre-processed picture data 19. For example, the pre-processing performed by pre-processing unit 18 may include trimming, color format conversion (e.g., from RGB to YCbCr), toning, or denoising. It is to be understood that the pre-processing unit 18 may be an optional component.

Encoder 20, e.g., video encoder 20, is used to receive pre-processed picture data 19 and provide encoded picture data 21 (details will be described further below, e.g., based on fig. 3 or fig. 5). In one example, the encoder 20 may be used to perform embodiments one through seven described below.

Communication interface 22 of source device 12 may be used to receive encoded picture data 21 and transmit to other devices, e.g., destination device 14 or any other device for storage or direct reconstruction, or to process encoded picture data 21 prior to correspondingly storing encoded data 13 and/or transmitting encoded data 13 to other devices, e.g., destination device 14 or any other device for decoding or storage.

Destination device 14 includes a decoder 30 (e.g., a video decoder 30), and may additionally, that is, optionally, include a communication interface or unit 28, a post-processing unit 32, and a display device 34.

Communication interface 28 of destination device 14 is used, for example, to receive encoded picture data 21 or encoded data 13 directly from source device 12 or any other source, such as a storage device, such as an encoded picture data storage device.

Communication interface 22 and communication interface 28 may be used to transmit or receive encoded picture data 21 or encoded data 13 by way of a direct communication link between source device 12 and destination device 14, such as a direct wired or wireless connection, or by way of any type of network, such as a wired or wireless network or any combination thereof, or any type of private and public networks, or any combination thereof.

Communication interface 22 may, for example, be used to encapsulate encoded picture data 21 into a suitable format, such as a packet, for transmission over a communication link or communication network.

Communication interface 28, which forms a corresponding part of communication interface 22, may for example be used to decapsulate encoded data 13 to obtain encoded picture data 21.

Both communication interface 22 and communication interface 28 may be configured as a unidirectional communication interface, as indicated by the arrow from source device 12 to destination device 14 for encoded picture data 13 in fig. 1, or as a bidirectional communication interface, and may be used, for example, to send and receive messages to establish a connection, acknowledge and exchange any other information related to a communication link and/or a data transmission, for example, an encoded picture data transmission.

Decoder 30 is used to receive encoded picture data 21 and provide decoded picture data 31 or decoded picture 31 (details will be described further below, e.g., based on fig. 4 or fig. 6). In one example, the decoder 30 may be used to perform embodiments one through seven described below.

Post-processor 32 of destination device 14 is used to post-process decoded picture data 31 (also referred to as reconstructed picture data), e.g., decoded picture 131, to obtain post-processed picture data 33, e.g., post-processed picture 33. Post-processing performed by post-processing unit 32 may include, for example, color format conversion (e.g., from YCbCr to RGB), toning, cropping, or resampling, or any other processing for, for example, preparing decoded picture data 31 for display by display device 34.

Display device 34 of destination device 14 is used to receive post-processed picture data 33 to display a picture to, for example, a user or viewer. Display device 34 may be or may include any type of display for presenting the reconstructed picture, such as an integrated or external display or monitor. For example, the display may include a Liquid Crystal Display (LCD), an Organic Light Emitting Diode (OLED) display, a plasma display, a projector, a micro LED display, a liquid crystal on silicon (LCoS), a Digital Light Processor (DLP), or any other display of any kind.

Although fig. 1 depicts source apparatus 12 and destination apparatus 14 as separate apparatuses, an apparatus embodiment may also include the functionality of both source apparatus 12 and destination apparatus 14 or both, i.e., source apparatus 12 or corresponding functionality and destination apparatus 14 or corresponding functionality. In such embodiments, source device 12 or corresponding functionality and destination device 14 or corresponding functionality may be implemented using the same hardware and/or software, or using separate hardware and/or software, or any combination thereof.

It will be apparent to those skilled in the art from this description that the existence and (exact) division of the functionality of the different elements or source device 12 and/or destination device 14 shown in fig. 1 may vary depending on the actual device and application.

Encoder 20 (e.g., video encoder 20) and decoder 30 (e.g., video decoder 30) may each be implemented as any of a variety of suitable circuitry, such as one or more microprocessors, Digital Signal Processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic, hardware, or any combinations thereof. If the techniques are implemented in part in software, an apparatus may store instructions of the software in a suitable non-transitory computer-readable storage medium and may execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Any of the foregoing, including hardware, software, a combination of hardware and software, etc., may be considered one or more processors. Each of video encoder 20 and video decoder 30 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder/decoder (codec) in a corresponding device.

Source device 12 may be referred to as a video encoding device or a video encoding apparatus. Destination device 14 may be referred to as a video decoding device or a video decoding apparatus. Source device 12 and destination device 14 may be examples of video encoding devices or video encoding apparatus.

Source device 12 and destination device 14 may comprise any of a variety of devices, including any type of handheld or stationary device, such as a notebook or laptop computer, a mobile phone, a smart phone, a tablet or tablet computer, a camcorder, a desktop computer, a set-top box, a television, a display device, a digital media player, a video game console, a video streaming device (e.g., a content service server or a content distribution server), a broadcast receiver device, a broadcast transmitter device, etc., and may not use or use any type of operating system.

In some cases, source device 12 and destination device 14 may be equipped for wireless communication. Thus, source device 12 and destination device 14 may be wireless communication devices.

In some cases, the video encoding system 10 shown in fig. 1 is merely an example, and the techniques of this application may be applicable to video encoding settings (e.g., video encoding or video decoding) that do not necessarily involve any data communication between the encoding and decoding devices. In other examples, the data may be retrieved from local storage, streamed over a network, and so on. A video encoding device may encode and store data to a memory, and/or a video decoding device may retrieve and decode data from a memory. In some examples, the encoding and decoding are performed by devices that do not communicate with each other, but merely encode data to and/or retrieve data from memory and decode data.

It should be understood that for each of the examples described above with reference to video encoder 20, video decoder 30 may be used to perform the reverse process. With respect to signaling syntax elements, video decoder 30 may be configured to receive and parse such syntax elements and decode the associated video data accordingly. In some examples, video encoder 20 may entropy encode the syntax elements into an encoded video bitstream. In such instances, video decoder 30 may parse such syntax elements and decode the relevant video data accordingly.

Fig. 2 is an illustration of an example of a video encoding system 40 including encoder 20 of fig. 3 and/or decoder 30 of fig. 4, according to an example embodiment. System 40 may implement a combination of the various techniques of the present application. In the illustrated embodiment, video encoding system 40 may include an imaging device 41, video encoder 20, video decoder 30 (and/or a video encoder implemented by logic 47 of processing unit 46), an antenna 42, one or more processors 43, one or more memories 44, and/or a display device 45.

As shown in fig. 2, the imaging device 41, the antenna 42, the processing unit 46, the logic circuit 47, the video encoder 20, the video decoder 30, the processor 43, the memory 44, and/or the display device 45 are capable of communicating with each other. As discussed, although video encoding system 40 is depicted with video encoder 20 and video decoder 30, in different examples, video encoding system 40 may include only video encoder 20 or only video decoder 30.

In some examples, as shown in fig. 2, video encoding system 40 may include an antenna 42. For example, the antenna 42 may be used to transmit or receive an encoded bitstream of video data. Additionally, in some examples, video encoding system 40 may include a display device 45. Display device 45 may be used to present video data. In some examples, as shown in fig. 2, logic 47 may be implemented by processing unit 46. The processing unit 46 may comprise application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, or the like. Video coding system 40 may also include an optional processor 43, which optional processor 43 similarly may include application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, or the like. In some examples, the logic 47 may be implemented in hardware, such as video encoding specific hardware, and the processor 43 may be implemented in general purpose software, an operating system, and so on. In addition, the Memory 44 may be any type of Memory, such as a volatile Memory (e.g., Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), etc.) or a nonvolatile Memory (e.g., flash Memory, etc.), and the like. In a non-limiting example, storage 44 may be implemented by a speed cache memory. In some instances, logic circuitry 47 may access memory 44 (e.g., to implement an image buffer). In other examples, logic 47 and/or processing unit 46 may include memory (e.g., cache, etc.) for implementing image buffers, etc.

In some examples, video encoder 20 implemented by logic circuitry may include an image buffer (e.g., implemented by processing unit 46 or memory 44) and a graphics processing unit (e.g., implemented by processing unit 46). The graphics processing unit may be communicatively coupled to the image buffer. The graphics processing unit may include video encoder 20 implemented by logic circuitry 47 to implement the various modules discussed with reference to fig. 2 and/or any other encoder system or subsystem described herein. Logic circuitry may be used to perform various operations discussed herein.

Video decoder 30 may be implemented in a similar manner by logic circuitry 47 to implement the various modules discussed with reference to decoder 30 of fig. 4 and/or any other decoder system or subsystem described herein. In some examples, logic circuit implemented video decoder 30 may include an image buffer (implemented by processing unit 2820 or memory 44) and a graphics processing unit (e.g., implemented by processing unit 46). The graphics processing unit may be communicatively coupled to the image buffer. The graphics processing unit may include video decoder 30 implemented by logic circuitry 47 to implement the various modules discussed with reference to fig. 4 and/or any other decoder system or subsystem described herein.

In some examples, antenna 42 of video encoding system 40 may be used to receive an encoded bitstream of video data. As discussed, the encoded bitstream may include data related to the encoded video frame, indicators, index values, mode selection data, etc., discussed herein, such as data related to the encoding partition (e.g., transform coefficients or quantized transform coefficients, (as discussed) optional indicators, and/or data defining the encoding partition). Video encoding system 40 may also include a video decoder 30 coupled to antenna 42 and configured to decode the encoded bitstream. The display device 45 is used to present video frames.

Encoder and encoding method

Fig. 3 shows a schematic/conceptual block diagram of an example of a video encoder 20 for implementing the techniques of this application. In the example of fig. 3, video encoder 20 includes a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a buffer 216, a loop filter unit 220, a Decoded Picture Buffer (DPB) 230, a prediction processing unit 260, and an entropy encoding unit 270. Prediction processing unit 260 may include inter prediction unit 244, intra prediction unit 254, and mode selection unit 262. Inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 shown in fig. 3 may also be referred to as a hybrid video encoder or a video encoder according to a hybrid video codec.

For example, the residual calculation unit 204, the transform processing unit 206, the quantization unit 208, the prediction processing unit 260, and the entropy encoding unit 270 form a forward signal path of the encoder 20, and, for example, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the Decoded Picture Buffer (DPB) 230, the prediction processing unit 260 form a backward signal path of the encoder, wherein the backward signal path of the encoder corresponds to a signal path of a decoder (see the decoder 30 in fig. 4).

Encoder 20 receives picture 201 or block 203 of picture 201, e.g., a picture in a sequence of pictures forming a video or video sequence, e.g., via input 202. Picture block 203 may also be referred to as a current picture block or a picture block to be encoded, and picture 201 may be referred to as a current picture or a picture to be encoded (especially when the current picture is distinguished from other pictures in video encoding, such as previously encoded and/or decoded pictures in the same video sequence, i.e., a video sequence that also includes the current picture).

Segmentation

An embodiment of encoder 20 may include a partitioning unit (not shown in fig. 3) for partitioning picture 201 into a plurality of blocks, such as block 203, typically into a plurality of non-overlapping blocks. The partitioning unit may be used to use the same block size for all pictures in a video sequence and a corresponding grid defining the block size, or to alter the block size between pictures or subsets or groups of pictures and partition each picture into corresponding blocks.

In one example, prediction processing unit 260 of video encoder 20 may be used to perform any combination of the above-described segmentation techniques.

Like picture 201, block 203 is also or can be viewed as a two-dimensional array or matrix of sample points having intensity values (sample values), although smaller in size than picture 201. In other words, the block 203 may comprise, for example, one sample array (e.g., a luma array in the case of a black and white picture 201) or three sample arrays (e.g., a luma array and two chroma arrays in the case of a color picture) or any other number and/or class of arrays depending on the color format applied. The number of sampling points in the horizontal and vertical directions (or axes) of the block 203 defines the size of the block 203.

The encoder 20 as shown in fig. 3 is used to encode the picture 201 block by block, e.g., performing encoding and prediction for each block 203.

Residual calculation

The residual calculation unit 204 is configured to calculate a residual block 205 based on the picture block 203 and the prediction block 265 (further details of the prediction block 265 are provided below), e.g. by subtracting sample values of the picture block 203 from sample values of the prediction block 265 on a sample-by-sample (pixel-by-pixel) basis to obtain the residual block 205 in the sample domain.

Transformation of

The transform processing unit 206 is configured to apply a transform, such as a Discrete Cosine Transform (DCT) or a Discrete Sine Transform (DST), on the sample values of the residual block 205 to obtain transform coefficients 207 in a transform domain. The transform coefficients 207 may also be referred to as transform residual coefficients and represent the residual block 205 in the transform domain.

The transform processing unit 206 may be used to apply integer approximations of DCT/DST, such as the transform specified for HEVC/h.265. Such integer approximations are typically scaled by some factor compared to the orthogonal DCT transform. To maintain the norm of the residual block processed by the forward transform and the inverse transform, an additional scaling factor is applied as part of the transform process. The scaling factor is typically selected based on certain constraints, e.g., the scaling factor is a power of 2 for a shift operation, a trade-off between bit depth of transform coefficients, accuracy and implementation cost, etc. For example, a specific scaling factor may be specified on the decoder 30 side for the inverse transform by, for example, inverse transform processing unit 212 (and on the encoder 20 side for the corresponding inverse transform by, for example, inverse transform processing unit 212), and correspondingly, a corresponding scaling factor may be specified on the encoder 20 side for the forward transform by transform processing unit 206.

Quantization

Quantization unit 208 is used to quantize transform coefficients 207, e.g., by applying scalar quantization or vector quantization, to obtain quantized transform coefficients 209. Quantized transform coefficients 209 may also be referred to as quantized residual coefficients 209. The quantization process may reduce the bit depth associated with some or all of transform coefficients 207. For example, an n-bit transform coefficient may be rounded down to an m-bit transform coefficient during quantization, where n is greater than m. The quantization level may be modified by adjusting a Quantization Parameter (QP). For example, for scalar quantization, different scales may be applied to achieve finer or coarser quantization. Smaller quantization steps correspond to finer quantization and larger quantization steps correspond to coarser quantization. An appropriate quantization step size may be indicated by a Quantization Parameter (QP). For example, the quantization parameter may be an index of a predefined set of suitable quantization step sizes. For example, a smaller quantization parameter may correspond to a fine quantization (smaller quantization step size) and a larger quantization parameter may correspond to a coarse quantization (larger quantization step size), or vice versa. The quantization may comprise a division by a quantization step size and a corresponding quantization or inverse quantization, e.g. performed by inverse quantization 210, or may comprise a multiplication by a quantization step size. Embodiments according to some standards, such as HEVC, may use a quantization parameter to determine the quantization step size. In general, the quantization step size may be calculated based on the quantization parameter using a fixed point approximation of an equation that includes division. Additional scaling factors may be introduced for quantization and dequantization to recover the norm of the residual block that may be modified due to the scale used in the fixed point approximation of the equation for the quantization step size and quantization parameter. In one example implementation, the inverse transform and inverse quantization scales may be combined. Alternatively, a custom quantization table may be used and signaled from the encoder to the decoder, e.g., in a bitstream. Quantization is a lossy operation, where the larger the quantization step size, the greater the loss.

The inverse quantization unit 210 is configured to apply inverse quantization of the quantization unit 208 on the quantized coefficients to obtain inverse quantized coefficients 211, e.g., to apply an inverse quantization scheme of the quantization scheme applied by the quantization unit 208 based on or using the same quantization step as the quantization unit 208. The dequantized coefficients 211 may also be referred to as dequantized residual coefficients 211, corresponding to transform coefficients 207, although the loss due to quantization is typically not the same as the transform coefficients.

The inverse transform processing unit 212 is configured to apply an inverse transform of the transform applied by the transform processing unit 206, for example, an inverse Discrete Cosine Transform (DCT) or an inverse Discrete Sine Transform (DST), to obtain an inverse transform block 213 in the sample domain. The inverse transform block 213 may also be referred to as an inverse transform dequantized block 213 or an inverse transform residual block 213.

The reconstruction unit 214 (e.g., summer 214) is used to add the inverse transform block 213 (i.e., the reconstructed residual block 213) to the prediction block 265 to obtain the reconstructed block 215 in the sample domain, e.g., to add sample values of the reconstructed residual block 213 to sample values of the prediction block 265.

Optionally, a buffer unit 216 (or simply "buffer" 216), such as a line buffer 216, is used to buffer or store the reconstructed block 215 and corresponding sample values, for example, for intra prediction. In other embodiments, the encoder may be used to use the unfiltered reconstructed block and/or corresponding sample values stored in buffer unit 216 for any class of estimation and/or prediction, such as intra prediction.

For example, an embodiment of encoder 20 may be configured such that buffer unit 216 is used not only to store reconstructed blocks 215 for intra prediction 254, but also for loop filter unit 220 (not shown in fig. 3), and/or such that buffer unit 216 and decoded picture buffer unit 230 form one buffer, for example. Other embodiments may be used to use filtered block 221 and/or blocks or samples from decoded picture buffer 230 (neither shown in fig. 3) as input or basis for intra prediction 254.

The loop filter unit 220 (or simply "loop filter" 220) is used to filter the reconstructed block 215 to obtain a filtered block 221, so as to facilitate pixel transition or improve video quality. Loop filter unit 220 is intended to represent one or more loop filters, such as a deblocking filter, a sample-adaptive offset (SAO) filter, or other filters, such as a bilateral filter, an Adaptive Loop Filter (ALF), or a sharpening or smoothing filter, or a collaborative filter. Although loop filter unit 220 is shown in fig. 3 as an in-loop filter, in other configurations, loop filter unit 220 may be implemented as a post-loop filter. The filtered block 221 may also be referred to as a filtered reconstructed block 221. The decoded picture buffer 230 may store the reconstructed encoded block after the loop filter unit 220 performs a filtering operation on the reconstructed encoded block.

Embodiments of encoder 20 (correspondingly, loop filter unit 220) may be configured to output loop filter parameters (e.g., sample adaptive offset information), e.g., directly or after entropy encoding by entropy encoding unit 270 or any other entropy encoding unit, e.g., such that decoder 30 may receive and apply the same loop filter parameters for decoding.

Decoded Picture Buffer (DPB) 230 may be a reference picture memory that stores reference picture data for use by video encoder 20 in encoding video data. DPB 230 may be formed from any of a variety of memory devices, such as Dynamic Random Access Memory (DRAM) including Synchronous DRAM (SDRAM), Magnetoresistive RAM (MRAM), Resistive RAM (RRAM), or other types of memory devices. The DPB 230 and the buffer 216 may be provided by the same memory device or separate memory devices. In a certain example, a Decoded Picture Buffer (DPB) 230 is used to store filtered blocks 221. Decoded picture buffer 230 may further be used to store other previous filtered blocks, such as previous reconstructed and filtered blocks 221, of the same current picture or of a different picture, such as a previous reconstructed picture, and may provide the complete previous reconstructed, i.e., decoded picture (and corresponding reference blocks and samples) and/or the partially reconstructed current picture (and corresponding reference blocks and samples), e.g., for inter prediction. In a certain example, if reconstructed block 215 is reconstructed without in-loop filtering, Decoded Picture Buffer (DPB) 230 is used to store reconstructed block 215.

Prediction processing unit 260, also referred to as block prediction processing unit 260, is used to receive or obtain block 203 (current block 203 of current picture 201) and reconstructed picture data, e.g., reference samples of the same (current) picture from buffer 216 and/or reference picture data 231 of one or more previously decoded pictures from decoded picture buffer 230, and to process such data for prediction, i.e., to provide prediction block 265, which may be inter-predicted block 245 or intra-predicted block 255.

The mode selection unit 262 may be used to select a prediction mode (e.g., intra or inter prediction mode) and/or a corresponding prediction block 245 or 255 used as the prediction block 265 to calculate the residual block 205 and reconstruct the reconstructed block 215.

Embodiments of mode selection unit 262 may be used to select prediction modes (e.g., from those supported by prediction processing unit 260) that provide the best match or the smallest residual (smallest residual means better compression in transmission or storage), or that provide the smallest signaling overhead (smallest signaling overhead means better compression in transmission or storage), or both. The mode selection unit 262 may be configured to determine a prediction mode based on Rate Distortion Optimization (RDO), i.e., select a prediction mode that provides the minimum rate distortion optimization, or select a prediction mode in which the associated rate distortion at least meets the prediction mode selection criteria.

The prediction processing performed by the example of the encoder 20 (e.g., by the prediction processing unit 260) and the mode selection performed (e.g., by the mode selection unit 262) will be explained in detail below.

As described above, the encoder 20 is configured to determine or select the best or optimal prediction mode from a set of (predetermined) prediction modes. The prediction mode set may include, for example, intra prediction modes and/or inter prediction modes.

The intra prediction mode set may include 35 different intra prediction modes, or may include 67 different intra prediction modes, or may include an intra prediction mode defined in h.266 under development.

The set of inter prediction modes depends on the available reference pictures (i.e., at least partially decoded pictures stored in the DBP 230, for example, as described above) and other inter prediction parameters, e.g., on whether the best matching reference block is searched using the entire reference picture or only a portion of the reference picture, e.g., a search window region of a region surrounding the current block, and/or whether pixel interpolation, such as half-pixel and/or quarter-pixel interpolation, is applied, for example.

In addition to the above prediction mode, a skip mode and/or a direct mode may also be applied.

The prediction processing unit 260 may further be configured to partition the block 203 into smaller block partitions or sub-blocks, for example, by iteratively using quad-tree (QT) partitions, binary-tree (BT) partitions, or triple-tree (TT) partitions, or any combination thereof, and to perform prediction, for example, for each of the block partitions or sub-blocks, wherein mode selection includes selecting a tree structure of the partitioned block 203 and selecting a prediction mode to apply to each of the block partitions or sub-blocks.

The inter prediction unit 244 may include a Motion Estimation (ME) unit (not shown in fig. 3) and a Motion Compensation (MC) unit (not shown in fig. 3). The motion estimation unit is used to receive or obtain picture block 203 (current picture block 203 of current picture 201) and decoded picture 231, or at least one or more previously reconstructed blocks, e.g., reconstructed blocks of one or more other/different previously decoded pictures 231, for motion estimation. For example, the video sequence may comprise a current picture and a previously decoded picture 31, or in other words, the current picture and the previously decoded picture 31 may be part of, or form, a sequence of pictures forming the video sequence.

For example, the encoder 20 may be configured to select a reference block from a plurality of reference blocks of the same or different one of a plurality of other pictures and provide the reference picture and/or an offset (spatial offset) between a position (X, Y coordinates) of the reference block and a position of the current block to a motion estimation unit (not shown in fig. 3) as an inter prediction parameter. This offset is also called a Motion Vector (MV).

The motion compensation unit is used to obtain, e.g., receive, inter-prediction parameters and perform inter-prediction based on or using the inter-prediction parameters to obtain the inter-prediction block 245. The motion compensation performed by the motion compensation unit (not shown in fig. 3) may involve taking or generating a prediction block based on a motion/block vector determined by motion estimation (possibly performing interpolation to sub-pixel precision). Interpolation filtering may generate additional pixel samples from known pixel samples, potentially increasing the number of candidate prediction blocks that may be used to encode a picture block. Upon receiving the motion vector for the PU of the current picture block, motion compensation unit 246 may locate the prediction block in one reference picture list to which the motion vector points. Motion compensation unit 246 may also generate syntax elements associated with the blocks and video slices for use by video decoder 30 in decoding picture blocks of the video slices.

The intra prediction unit 254 is used to obtain, e.g., receive, the picture block 203 (current picture block) of the same picture and one or more previously reconstructed blocks, e.g., reconstructed neighboring blocks, for intra estimation. For example, encoder 20 may be used to select an intra-prediction mode from a plurality of intra-prediction modes.

Embodiments of encoder 20 may be used to select an intra prediction mode based on optimization criteria, such as based on a minimum residual (e.g., an intra prediction mode that provides a prediction block 255 that is most similar to current picture block 203) or a minimum code rate distortion.

The intra-prediction unit 254 is further configured to determine the intra-prediction block 255 based on the intra-prediction parameters as the selected intra-prediction mode. In any case, after selecting the intra-prediction mode for the block, intra-prediction unit 254 is also used to provide intra-prediction parameters, i.e., information indicating the selected intra-prediction mode for the block, to entropy encoding unit 270. In one example, intra-prediction unit 254 may be used to perform any combination of the intra-prediction techniques described below.

Entropy encoding unit 270 is configured to apply an entropy encoding algorithm or scheme (e.g., a Variable Length Coding (VLC) scheme, a Context Adaptive VLC (CAVLC) scheme, an arithmetic coding scheme, a Context Adaptive Binary Arithmetic Coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), Probability Interval Partitioning Entropy (PIPE) coding, or other entropy encoding methods or techniques) to individual or all of quantized residual coefficients 209, inter-prediction parameters, intra-prediction parameters, and/or loop filter parameters (or not) to obtain encoded picture data 21 that may be output by output 272 in the form of, for example, encoded bitstream 21. The encoded bitstream may be transmitted to video decoder 30, or archived for later transmission or retrieval by video decoder 30. Entropy encoding unit 270 may also be used to entropy encode other syntax elements of the current video slice being encoded.

Other structural variations of video encoder 20 may be used to encode the video stream. For example, the non-transform based encoder 20 may quantize the residual signal directly without the transform processing unit 206 for certain blocks or frames. In another embodiment, encoder 20 may have quantization unit 208 and inverse quantization unit 210 combined into a single unit.

Fig. 4 illustrates an exemplary video decoder 30 for implementing the techniques of the present application. Video decoder 30 is operative to receive encoded picture data (e.g., an encoded bitstream) 21, e.g., encoded by encoder 20, to obtain a decoded picture 231. During the decoding process, video decoder 30 receives video data, such as an encoded video bitstream representing picture blocks of an encoded video slice and associated syntax elements, from video encoder 20.

In the example of fig. 4, decoder 30 includes entropy decoding unit 304, inverse quantization unit 310, inverse transform processing unit 312, reconstruction unit 314 (e.g., summer 314), buffer 316, loop filter 320, decoded picture buffer 330, and prediction processing unit 360. The prediction processing unit 360 may include an inter prediction unit 344, an intra prediction unit 354, and a mode selection unit 362. In some examples, video decoder 30 may perform a decoding pass that is substantially reciprocal to the encoding pass described with reference to video encoder 20 of fig. 3.

Entropy decoding unit 304 is to perform entropy decoding on encoded picture data 21 to obtain, for example, quantized coefficients 309 and/or decoded encoding parameters (not shown in fig. 4), e.g., any or all of inter-prediction, intra-prediction parameters, loop filter parameters, and/or other syntax elements (decoded). The entropy decoding unit 304 is further for forwarding the inter-prediction parameters, the intra-prediction parameters, and/or other syntax elements to the prediction processing unit 360. Video decoder 30 may receive syntax elements at the video slice level and/or the video block level.

Inverse quantization unit 310 may be functionally identical to inverse quantization unit 110, inverse transform processing unit 312 may be functionally identical to inverse transform processing unit 212, reconstruction unit 314 may be functionally identical to reconstruction unit 214, buffer 316 may be functionally identical to buffer 216, loop filter 320 may be functionally identical to loop filter 220, and decoded picture buffer 330 may be functionally identical to decoded picture buffer 230.

Prediction processing unit 360 may include inter prediction unit 344 and intra prediction unit 354, where inter prediction unit 344 may be functionally similar to inter prediction unit 244 and intra prediction unit 354 may be functionally similar to intra prediction unit 254. The prediction processing unit 360 is typically used to perform block prediction and/or to obtain a prediction block 365 from the encoded data 21, as well as to receive or obtain (explicitly or implicitly) prediction related parameters and/or information about the selected prediction mode from, for example, the entropy decoding unit 304.

When the video slice is encoded as an intra-coded (I) slice, intra-prediction unit 354 of prediction processing unit 360 is used to generate a prediction block 365 for the picture block of the current video slice based on the signaled intra-prediction mode and data from previously decoded blocks of the current frame or picture. When a video frame is encoded as an inter-coded (i.e., B or P) slice, inter prediction unit 344 (e.g., a motion compensation unit) of prediction processing unit 360 is used to generate a prediction block 365 for the video block of the current video slice based on the motion vectors and other syntax elements received from entropy decoding unit 304. For inter prediction, a prediction block may be generated from one reference picture within one reference picture list. Video decoder 30 may construct the reference frame list using default construction techniques based on the reference pictures stored in DPB 330: list 0 and list 1.

Prediction processing unit 360 is used to determine prediction information for the video blocks of the current video slice by parsing the motion vectors and other syntax elements, and to generate a prediction block for the current video block being decoded using the prediction information. For example, prediction processing unit 360 uses some of the syntax elements received to determine a prediction mode (e.g., intra or inter prediction) for encoding video blocks of a video slice, an inter prediction slice type (e.g., B-slice, P-slice, or GPB-slice), construction information for one or more of a reference picture list of the slice, a motion vector for each inter-coded video block of the slice, an inter prediction state for each inter-coded video block of the slice, and other information to decode video blocks of the current video slice.

Inverse quantization unit 310 may be used to inverse quantize (i.e., inverse quantize) the quantized transform coefficients provided in the bitstream and decoded by entropy decoding unit 304. The inverse quantization process may include using quantization parameters calculated by video encoder 20 for each video block in the video slice to determine the degree of quantization that should be applied and likewise the degree of inverse quantization that should be applied.

Inverse transform processing unit 312 is used to apply an inverse transform (e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process) to the transform coefficients in order to produce a block of residuals in the pixel domain.

The reconstruction unit 314 (e.g., summer 314) is used to add the inverse transform block 313 (i.e., reconstructed residual block 313) to the prediction block 365 to obtain the reconstructed block 315 in the sample domain, e.g., by adding sample values of the reconstructed residual block 313 to sample values of the prediction block 365.

Loop filter unit 320 (either during or after the encoding cycle) is used to filter reconstructed block 315 to obtain filtered block 321 to facilitate pixel transitions or improve video quality. In one example, loop filter unit 320 may be used to perform any combination of the filtering techniques described below. Loop filter unit 320 is intended to represent one or more loop filters, such as a deblocking filter, a sample-adaptive offset (SAO) filter, or other filters, such as a bilateral filter, an Adaptive Loop Filter (ALF), or a sharpening or smoothing filter, or a collaborative filter. Although loop filter unit 320 is shown in fig. 4 as an in-loop filter, in other configurations, loop filter unit 320 may be implemented as a post-loop filter.

Decoded video block 321 in a given frame or picture is then stored in decoded picture buffer 330, which stores reference pictures for subsequent motion compensation.

Decoder 30 is used to output decoded picture 31, e.g., via output 332, for presentation to or viewing by a user.

Other variations of video decoder 30 may be used to decode the compressed bitstream. For example, decoder 30 may generate an output video stream without loop filter unit 320. For example, the non-transform based decoder 30 may directly inverse quantize the residual signal without the inverse transform processing unit 312 for certain blocks or frames. In another embodiment, video decoder 30 may have inverse quantization unit 310 and inverse transform processing unit 312 combined into a single unit.

Fig. 5 is a schematic structural diagram of a video coding apparatus 400 (e.g., the video encoding apparatus 400 or the video decoding apparatus 400) according to an embodiment of the present application. Video coding apparatus 400 is suitable for implementing the embodiments described herein. In one embodiment, video coding device 400 may be a video decoder (e.g., video decoder 30 of fig. 1) or a video encoder (e.g., video encoder 20 of fig. 1). In another embodiment, video coding device 400 may be one or more components of video decoder 30 of fig. 1 or video encoder 20 of fig. 1 described above.

Video coding apparatus 400 includes: an ingress port 410 and a reception unit (Rx)420 for receiving data, a processor, logic unit or Central Processing Unit (CPU)430 for processing data, a transmitter unit (Tx)440 and an egress port 450 for transmitting data, and a memory 460 for storing data. Video coding device 400 may also include optical-to-Electrical (EO) components and optical-to-electrical (opto) components coupled with ingress port 410, receiver unit 420, transmitter unit 440, and egress port 450 for egress or ingress of optical or electrical signals.

The processor 430 is implemented by hardware and software. Processor 430 may be implemented as one or more CPU chips, cores (e.g., multi-core processors), FPGAs, ASICs, and DSPs. Processor 430 is in communication with inlet port 410, receiver unit 420, transmitter unit 440, outlet port 450, and memory 460. Processor 430 includes a coding module 470 (e.g., encoding module 470 or decoding module 470). The encoding/decoding module 470 implements the embodiments disclosed above. For example, the encoding/decoding module 470 implements, processes, or provides various encoding operations. Accordingly, substantial improvements are provided to the functionality of the video coding apparatus 400 by the encoding/decoding module 470 and affect the transition of the video coding apparatus 400 to different states. Alternatively, the encode/decode module 470 is implemented as instructions stored in the memory 460 and executed by the processor 430.

The memory 460, which may include one or more disks, tape drives, and solid state drives, may be used as an over-flow data storage device for storing programs when such programs are selectively executed, and for storing instructions and data that are read during program execution. The memory 460 may be volatile and/or nonvolatile, and may be Read Only Memory (ROM), Random Access Memory (RAM), random access memory (TCAM), and/or Static Random Access Memory (SRAM).

Fig. 6 is a simplified block diagram of an apparatus 500 that may be used as either or both of source device 12 and destination device 14 in fig. 1, according to an example embodiment. Apparatus 500 may implement the techniques of this application, and apparatus 500 for implementing chroma block prediction may take the form of a computing system including multiple computing devices, or a single computing device such as a mobile phone, tablet computer, laptop computer, notebook computer, desktop computer, or the like.

The processor 502 in the apparatus 500 may be a central processor. Alternatively, processor 502 may be any other type of device or devices now or later developed that is capable of manipulating or processing information. As shown in FIG. 6, although the disclosed embodiments may be practiced using a single processor, such as processor 502, speed and efficiency advantages may be realized using more than one processor.

In one embodiment, the Memory 504 of the apparatus 500 may be a Read Only Memory (ROM) device or a Random Access Memory (RAM) device. Any other suitable type of storage device may be used for memory 504. The memory 504 may include code and data 506 that is accessed by the processor 502 using a bus 512. The memory 504 may further include an operating system 508 and application programs 510, the application programs 510 including at least one program that permits the processor 502 to perform the methods described herein. For example, applications 510 may include applications 1 through N, applications 1 through N further including video coding applications that perform the methods described herein. The apparatus 500 may also include additional memory in the form of a slave memory 514, the slave memory 514 may be, for example, a memory card for use with a mobile computing device. Because a video communication session may contain a large amount of information, this information may be stored in whole or in part in the slave memory 514 and loaded into the memory 504 for processing as needed.

Device 500 may also include one or more output apparatuses, such as a display 518. In one example, display 518 may be a touch-sensitive display that combines a display and a touch-sensitive element operable to sense touch inputs. A display 518 may be coupled to the processor 502 via the bus 512. Other output devices that permit a user to program apparatus 500 or otherwise use apparatus 500 may be provided in addition to display 518, or other output devices may be provided as an alternative to display 518. When the output device is or includes a display, the display may be implemented in different ways, including by a Liquid Crystal Display (LCD), a Cathode Ray Tube (CRT) display, a plasma display, or a Light Emitting Diode (LED) display, such as an Organic LED (OLED) display.

The apparatus 500 may also include or be in communication with an image sensing device 520, the image sensing device 520 being, for example, a camera or any other image sensing device 520 now or later developed that can sense an image, such as an image of a user running the apparatus 500. The image sensing device 520 may be placed directly facing the user running the apparatus 500. In an example, the position and optical axis of image sensing device 520 may be configured such that its field of view includes an area proximate display 518 and display 518 is visible from that area.

The apparatus 500 may also include or be in communication with a sound sensing device 522, such as a microphone or any other sound sensing device now known or later developed that can sense sound in the vicinity of the apparatus 500. The sound sensing device 522 may be positioned to face directly the user operating the apparatus 500 and may be used to receive sounds, such as speech or other utterances, emitted by the user while operating the apparatus 500.

Although the processor 502 and memory 504 of the apparatus 500 are depicted in fig. 6 as being integrated in a single unit, other configurations may also be used. The operations of processor 502 may be distributed among multiple directly couplable machines (each machine having one or more processors), or distributed in a local area or other network. Memory 504 may be distributed among multiple machines, such as a network-based memory or a memory among multiple machines running apparatus 500. Although only a single bus is depicted here, the bus 512 of the device 500 may be formed from multiple buses. Further, the secondary memory 514 may be directly coupled to other components of the apparatus 500 or may be accessible over a network and may comprise a single integrated unit, such as one memory card, or multiple units, such as multiple memory cards. Accordingly, the apparatus 500 may be implemented in a variety of configurations.

As described earlier in this application, color video contains chrominance components (U, V) in addition to a luminance (Y) component. Therefore, in addition to encoding the luminance component, the chrominance component needs to be encoded. There are generally YUV4:4:4, YUV4:2:2, and YUV4:2:0, according to the sampling method of the luminance component and the chrominance component in color video. As shown in fig. 7, where the crosses represent luminance component sampling points and the circles represent chrominance component sampling points.

4:4:4 Format: indicating that the chrominance components have not been downsampled;

4:2:2 Format: indicating that the chrominance components are down-sampled 2:1 horizontally relative to the luminance components and not vertically. For every two U sampling points or V sampling points, each row comprises four Y sampling points;

4:2:0 Format: representing a 2:1 horizontal down-sampling of the chrominance components relative to the luminance components, and a 2:1 vertical down-sampling.

Of these, YUV4:2:0 is most common. In the case of a video image in YUV4:2:0 sampling format, if the luminance component of an image block is a 2Mx2N sized image block, the chrominance component of the image block is an MxN sized image block. Hence, the chroma components of an image block are also referred to in this application as chroma blocks or chroma component blocks. This application is described in YUV4:2:0, but may be applied to other sampling methods for luminance and chrominance components.

In the present application, a pixel point in a chrominance image (picture) is referred to as a chrominance sample point (chroma sample) for short, or a chrominance point; a pixel point in a luminance image (picture) is simply referred to as a luminance sample point (luma sample), or a luminance point.

Similar to the luminance component, the chroma intra-frame prediction also uses the boundary pixels of the adjacent reconstructed blocks around the current chroma block as the reference pixels of the current block, and maps the reference pixels to the pixel points in the current chroma block according to a certain prediction mode as the prediction values of the pixels in the current chroma block. In contrast, since the texture of the chroma component is generally simpler, the number of chroma component intra prediction modes is generally less than the luma component.

A Cross component prediction mode (CCP) is also called a Cross component intra prediction mode (CCIP) or a Cross Component Linear Mode (CCLM) prediction mode. The CCLM prediction mode may be referred to as a Linear Model (LM) mode. The LM mode (simply referred to as a linear model, or a linear mode) is a chrominance intra prediction method using a texture correlation between luminance and chrominance. The LM uses the reconstructed luma component to derive the current chroma block prediction value according to a linear model, which can be expressed as:

pred_C(i,j)＝α*recⁱ _L(i,j)+β (1)

alpha and beta are linear model coefficients, alpha is a scaling coefficient, and beta is an offset factor pred_C(i, j) is the predicted value of the chroma pixel at the (i, j) position, recⁱ _LAnd (i, j) is the luminance reconstruction pixel value at the position (i, j) after the luminance reconstruction block corresponding to the current chrominance block (hereinafter, referred to as the corresponding luminance block) is down-sampled to the resolution of the chrominance component. In the YUV4:2:0 format video, the resolution of the luminance component is 4 times (two times each width and height) the resolution of the chrominance component, and in order to obtain a luminance block having the same resolution as the chrominance block, the luminance component needs to be down-sampled to the chrominance resolution by the same down-sampling method as the chrominance component and then used.

The linear model coefficients do not need to be transmitted encoded, but are derived using edge pixels of neighboring reconstructed blocks of the current chroma block and luma pixels at positions corresponding to the edge pixels. Fig. 8 shows an embodiment of Cross Component Prediction (CCP). In fig. 8, recL is a reconstructed luma block (the current chroma block corresponds to a luma block and neighboring reference pixels), recL 'is a downsampled luma block, and recC' is a neighboring reconstructed reference pixel of the current chroma block. The size of the current chroma block is WxH, the neighboring reconstructed pixels on the upper and left sides of the current chroma block are used as reference pixels, the size of the corresponding luma block is 2Wx2H, and the luma block reference pixels are downsampled to chroma resolution, so as to obtain the pixel block shown in fig. 8 (b). The adjacent reference pixels in fig. 8(b) and 8(c) form a one-to-one correspondence relationship.

For convenience of explanation, the present application refers to adjacent upper and left sides for calculating linear model coefficients as templates (templates). The adjacent upper edge is called the upper template, and the adjacent left edge is called the left template. The chrominance sampling points in the upper template are called upper template chrominance points, the luminance sampling points in the upper template are called upper template luminance points, and the left template chrominance points and the left template luminance points are known similarly. The template brightness points and the template chroma points are in one-to-one correspondence, and the values of the sampling points form value pairs.

In the embodiment of the present application, the template represents a set of luminance points or chrominance points used for calculating coefficients of the linear model, wherein the luminance points generally need to be obtained by downsampling (since the resolution of luminance components is different from that of chrominance), and are denoted as Luma' samples. Chroma points (Chroma samples) are generally one or two rows of adjacent upper pixels and one or two columns of adjacent left pixels of a current Chroma block. Fig. 9 is a schematic diagram of the stencil using one row and one column, and fig. 10 is a schematic diagram of the stencil using two rows and two columns.

The LM mode can effectively use the correlation between the luminance component and the chrominance component, and the LM method is more flexible than the directional prediction mode, thereby providing a more accurate prediction signal for the chrominance component.

In addition, there is also a Multiple linear model (MMLM) mode, and there are a plurality of α and β. Taking two linear models as an example, there are two sets of linear model coefficients, α₁，β₁And alpha₂，β₂。

The embodiment of the present application provides a method for predicting a chroma block, where the embodiment of the present application takes intra prediction as CCLM as an example for description, and the following detailed description is provided for a processing flow shown in fig. 11 with reference to a specific implementation manner, where the process exists in both an encoding process and a decoding process, and the contents may be as follows:

step 1101, obtaining a maximum brightness value and a minimum brightness value in a brightness pixel corresponding to a pixel adjacent to the target chromaticity block, and obtaining a first chromaticity value corresponding to the maximum brightness value and a second chromaticity value corresponding to the minimum brightness value.

The target chroma block is any chroma block that is not encoded or decoded, and the pixels adjacent to the target chroma block refer to reference pixels of a reconstructed block adjacent to the target chroma block, which is shown in fig. 9 and 10.

In implementation, when determining the current chroma block (which may be referred to as a target chroma block), the encoding mode of the target chroma block may be determined, and if the encoding mode is CCLM, pixels adjacent to the target chroma block may be determined, and then the maximum luminance value maxY and the minimum luminance value minY of the luminance pixels corresponding to the pixels may be determined. And a chrominance value corresponding to the maximum luminance value (i.e., first chrominance value maxC) and a chrominance value corresponding to the minimum luminance value (i.e., second chrominance value minC) may be determined.

The chrominance value corresponding to the maximum luminance value indicates that the chrominance pixel is the first chrominance value when the luminance pixel is the maximum luminance value, and the chrominance value corresponding to the minimum luminance value indicates that the chrominance pixel is the second chrominance value when the luminance pixel is the minimum luminance value.

It should be noted that the "determining to the current chroma block" may be "encoding to the current chroma block" or "decoding to the current chroma block".

Step 1102, if a first difference between the maximum brightness value and the minimum brightness value is greater than 0, performing right shift processing on the first difference according to the number of valid bits of the first difference and a first preset bit-depth to obtain a second difference.

Wherein the first preset bit-depth is a bit-depth preset corresponding to the first difference and stored in the aforementioned apparatus.

In implementation, after the maximum luminance value and the minimum luminance value are acquired, a difference between the maximum luminance value and the minimum luminance value, that is, a first difference value may be determined. And then judging whether the first difference is larger than 0, if so, determining the number of effective bits of the first difference, and then performing right shift processing on the first difference by using the number of the first effective bits and a first preset bit-depth to obtain a second difference.

Optionally, the first preset bit-depth is smaller than the bit-depth of the luminance pixel.

In an implementation, the first preset bit-depth may be set to be smaller than the bit-depth of the luminance pixel, for example, the bit-depth of the luminance pixel is 8 bits, and the first preset bit-depth may be 1bit, 3 bits, 4 bits, 6 bits, and so on.

Step 1103, determining an intra prediction model parameter corresponding to the target chroma block according to the first chroma value, the second chroma value and the second difference value.

The intra prediction model parameters include a scaling factor and an offset factor.

In an implementation, after the second difference is obtained, the scaling factor and the offset factor corresponding to the target chroma block may be determined by using the first chroma value, the second chroma value and the second difference.

And 1104, determining the prediction information of the target chroma block according to the intra-frame prediction model parameters and the corresponding brightness reconstruction information of the target chroma block.

In implementation, after determining the intra prediction model parameter corresponding to the target chroma block, the luminance reconstruction information corresponding to the target chroma block may be obtained, and then the prediction information of the target chroma block is determined by using the intra prediction model parameter determined in step 1103 and the luminance reconstruction information corresponding to the target chroma block.

Step 1104 may optionally be followed by adding the residual signal to the prediction information determined in step 1104 to obtain a reconstructed signal of the current chroma block.

Another embodiment of the present application is described by taking intra prediction as CCLM as an example, and the present process exists in both the encoding process and the decoding process, as shown in fig. 12.

Step 1201, obtaining a maximum brightness value and a minimum brightness value in the brightness pixels corresponding to the pixels adjacent to the target chromaticity block, and obtaining a first chromaticity value corresponding to the maximum brightness value and a second chromaticity value corresponding to the minimum brightness value.

The process of step 1201 can be referred to the process of step 1101.

Step 1202, if the first difference between the maximum luminance value and the minimum luminance value is greater than 0, determining a third difference between the number of significant bits of the first difference and a first preset bit-depth.

In an implementation, a difference between the maximum luminance value and the minimum luminance value may be determined, which may be represented as a first difference, and then it may be determined whether the first difference is greater than 0, if the first difference is greater than 0, the number of significant bits of the first difference may be determined, and a first pre-stored bit-depth may be obtained. Then, the difference between the number of significant bits of the first difference and the first preset bit-depth is determined, which may be determined as a third difference. For example, the number of significant bits of the first difference value is 6, the first preset bit-depth is 3, and the third difference value may be determined to be 3.

In step 1203, if the third difference is greater than 0, performing right shift processing on the first difference according to the third difference to obtain a second difference.

In implementation, after the third difference is determined, it may be determined whether the third difference is greater than 0, and if the third difference is greater than 0, the first difference may be right-shifted according to the third difference to obtain a second difference. For example, the third difference is 3, and the first difference may be shifted to the right by 2 bits.

Optionally, the right shift process may be as follows:

and shifting the first difference value to the right by a third difference value to obtain a second difference value.

In an implementation, the first difference may be shifted to the right by a third difference bit to obtain a second difference. For example, assume that the first preset bit-depth of the first difference is 3 bits, if the first difference is 10001110, the number of significant bits is 8 bits, the third difference is 5, and the second difference is 100. If the first difference is 00001010, the significand is 4 bits, the third difference is 1, and the second difference is 101.

Thus, subsequent look-up table determination

And/or

(N is the preset value of the normalized shift parameter, diff is the second difference), the bit-depth of diff is reduced relative to the first difference, the number of diff values in the table will be reduced (the reason is explained later), the table lookup can be improved to determine

And/or

The speed of (2).

Step 1204, determining an intra prediction model parameter corresponding to the target chroma block according to the first chroma value, the second chroma value, a preset value of the normalized shift parameter, the second difference value and the minimum brightness value.

Wherein the normalized shift parameter is used for shift processing, and the preset value of the normalized shift parameter can be preset and stored in the above mentioned device.

In implementation, each chroma block using the CCLM corresponds to an intra prediction model parameter, which includes an offset factor and a scaling coefficient.

The scaling factor and the offset factor corresponding to the target chromaticity block can be determined according to the first chromaticity value, the second chromaticity value, the preset value of the normalized shift parameter, the second difference value, the minimum brightness value and a preset formula.

Optionally, the value of the normalized shift parameter may be adjusted to determine the intra-frame prediction model parameter, and the corresponding processing may be as follows:

and determining a scaling coefficient in the intra-frame prediction model parameter corresponding to the target chroma block according to the first chroma value, the second difference value and a preset value. And determining an offset factor in the intra-frame prediction model parameter corresponding to the target chroma block according to the scaling coefficient, the second chroma value, the target value of the normalized shift parameter and the minimum brightness value, wherein the target value of the normalized shift parameter is determined according to the preset value of the normalized shift parameter and the third difference value.

The normalized shift parameter is used for shift processing, and for example, one of the normalized shift parameters is 00001010, the target value of the normalized shift parameter is 1, and the right shift parameter is 00000101 after the right shift processing. The target value of the normalized shift parameter may be used in a subsequent process of determining prediction information (which may also be referred to as a prediction signal).

In an implementation, a preset value of the normalized shift parameter may be obtained, the preset value being a parameter value preset for the normalized shift parameter. The preset value of the normalized shift parameter may then be added to the second difference to obtain a target value of the normalized shift parameter.

Then, the first chrominance value, the second chrominance value, the preset value of the normalized shift parameter and the second difference value can be used to be input into a preset formula to obtain a scaling coefficient corresponding to the target chrominance block, and then the scaling coefficient, the target value of the normalized shift parameter and the minimum luminance value are input into another preset formula to obtain an offset factor corresponding to the target chrominance block.

In addition, if the second difference is less than or equal to 0, the target value of the normalized shift parameter is a preset value of the normalized shift parameter, and the preset value of the normalized shift parameter may be subsequently used to determine the prediction information.

Optionally, the preset value of the normalized shift parameter is a bit-depth of the first difference, or a bit-depth of the luminance pixel, or a sum of the bit-depth of the first difference and a second preset value, or a product of the bit-depth of the first difference and a third preset value, or a bit-depth of one byte.

In an implementation, the preset value of the normalized shift parameter may be set to bit-depth of the first difference value. The preset value of the normalized shift parameter may also be set to the bit-depth of the luminance pixel.

And step 1205, determining the prediction information of the target chroma block according to the intra-frame prediction model parameters and the brightness reconstruction information corresponding to the target chroma block.

In an implementation, after determining the scaling factor and offset factor of the target chroma block, a pre-stored formula for determining the prediction information may be obtained, namely predSamples [ x ] [ y ] ═ Clip1C (((pDsY [ x ] [ y ] × a) > k) + b), where predSamples [ x ] [ y ] is the prediction information of the target chroma block, pDsY [ x ] [ y ] is the value of the downsampled block corresponding to the luma block, Clip1C () is a limiting operation (so that the obtained pixel value is within the valid range), and k is the target value of the normalized shift parameter. In this equation, since pDsY x, a, and b are known quantities, predSamples x of the target chroma block, i.e., prediction information (which may also be referred to as a prediction signal) of the target chroma block, can be determined.

In this way, for each chroma block using the CCLM in each frame image, the prediction information is obtained in the above steps, and the prediction information of each chroma block using the CCLM in each frame image can be determined, and encoding or decoding processing can be performed.

Step 1205 optionally includes adding the residual signal to the prediction information determined in step 1205 to obtain a reconstructed signal of the current chroma block.

Optionally, in step 1204, there are various ways to determine the scaling factor and the offset factor, and this embodiment provides three possible ways:

the first method is as follows:

wherein a is a scaling coefficient, diff is a second difference value, maxC is a first chromaticity value, minC is a second chromaticity value, and N is a preset value. b minC- ((a minY) > k), wherein b is a shift factor, a is a scaling coefficient, minC is a second chromaticity value, minY is a minimum brightness value, and k is a target value.

In implementation, a preset scaling coefficient calculation formula can be obtained, that is

Then, the first chrominance value maxC, the second chrominance value minC, the preset value N of the normalized shift parameter and the second difference diff are substituted into the formula, so as to obtain the scaling coefficient a corresponding to the target chrominance block,

show that

The whole is taken down and taken up,

show that

And rounding down. For example, if N is 16, then

Then, a preset offset factor calculation formula may be obtained, that is, b is minC- ((a minY) > k), which represents that a difference is obtained between values after minC and a minY are shifted to the right by k bits, so as to obtain an offset factor b corresponding to the target chrominance block, and the scaling coefficient a, the second chrominance minC, the target value k of the normalized shift parameter, and the minimum luminance value minY may be substituted into the formula, so as to determine the offset factor b corresponding to the target chrominance block, where, in the first mode, k is N + shiftLuma, and shiftLuma is the third difference mentioned above.

In use, the composition is

When determining the scaling factor, diff satisfies the condition of greater than 0 when using this formula, since diff is in the denominator. When diff is not greater than 0, the scaling factor is 0 and the offset factor is a second chrominance value.

The pseudo code used in the processing procedure from step 1202 to mode one can be expressed as follows:

a-maxY-minY (meaning that the first difference (denoted by a) is the difference between the maximum luminance value and the minimum luminance value)

shiftLuma ═ (a ═ 0)? 0 Floor (Log2(Abs (A))) -DIFF _ BIT _ DEPTH (third difference (shiftLuma) is taken as 0 when the first difference is equal to 0, and Floor (Log2(Abs (A))) -DIFF _ BIT _ DEPTH is taken as absolute value when the first difference is equal to 0, DIFF _ BIT _ DEPTH is the first predetermined BIT-DEPTH)

shiftLuma ═ Max (0, shiftLuma) (meaning that the third difference shiftLuma takes the maximum of 0 and shiftLuma)

diff > shiftLuma (meaning that the first difference a is right-shifted by a third difference bit to obtain a second difference)

k is N + shiftLuma (meaning that the target value k of the normalized shift parameter is taken as the sum of the preset value N of the normalized shift parameter and the third difference)

If diff is larger than 0, the following is

Other, the following

a＝0

b＝minC-((a*minY)＞＞k)

Wherein the content of the first and second substances,

a scaling factor a, a second chromaticity maxC, a second chromaticity minC, a target value k and a minimum brightness value minY of the normalized shift parameter, a shift factor b, a second difference diff, a preset value N of the normalized shift parameter.

It should be noted that the above-mentioned language in parentheses after the description is used to explain the preceding sentence.

The second method comprises the following steps:

wherein a is a scaling coefficient, diff is a second difference value, maxC is a first chromaticity value, minC is a second chromaticity value, and N is a preset value. b minC- ((a minY) > k), wherein b is a shift factor, a is a scaling coefficient, minY is a minimum brightness value, and k is a target value.

Then the first chrominance value maxC, the second chrominance value minC, the preset value of the normalized shift parameter and the second difference diff are substituted into the formula, so as to obtain the scaling coefficient,

show that

And rounding down.

In use, the composition is

The pseudo code used in the processing of step 1202 to mode two can be expressed as follows:

If diff is larger than 0, the following is

Other, the following

a＝0

b＝minC-((a*minY)＞＞k)

The scaling factor a, the second chromaticity maxC, the second chromaticity minC, the target value k and the minimum brightness value minY of the normalized shift parameter, the offset factor b, the second difference diff, and the preset value N of the normalized shift parameter.

It should be noted that the above is determining

And

in the process, a table look-up mode is generally used for determining, if the bit-depth of the diff is 10 bits, the value range of the diff is 0-1023, and in all 1024 cases, if the value of the diff is taken as a column, 1024 columns and 2 columns exist¹⁶As a row, there is a row, i.e. a 1 x 1024 table, in which 2¹⁶Corresponding to each value of diff, there is a value corresponding to

The calculation result of (2). Thus, for

And

two tables are required, one for lookup

A table for looking up

The calculation result of (2).

In the first and second modes, the first difference a is shifted to the right to obtain the second differenceValue diff, therefore

Become as

Compared with the related art

Since the bit-depth of the denominator is reduced, the lookup determination can be improved

The table lookup speed can be increased because the reduction of the bit-depth of A reduces the number of all possible values of A in the table, e.g., if the bit-depth of A is 10 bits, the total number of tables is 2¹⁰The value of the seed is 2 bits in total in the table after the bit-depth of diff is changed to 3 bits³Values are taken so that the size of the table is reduced. In the first mode and the second mode, the first preset bit-depth bit is not directly shifted to the right of the A, but the difference value of the A and the first preset bit-depth is used as the bit number of the right shift, so that the effective bit of the A can be reserved as much as possible, and the coding and decoding performance is better.

In addition, both the first and second modes determine the scaling factor and the offset factor, but the second mode does not use the div parameter when determining the scaling factor, so that the second mode does not include the scaling factor and the offset factor

So that no look-up calculation is required

Then in the second mode, only one table may be stored for determining

The calculation result of (2). And since the div parameter is not used, there will be no

That is, there is no large number of multiplication operations, and the complexity of calculating the scaling factor can be reduced, so that the scaling factor can be determined quickly.

In addition, in the first embodiment, a may also be modified, that is, add an addDiff to a, where (shiftLuma)? 1 < (shiftLuma-1):0 (if shiftLuma is not equal to 0, then addDiff takes 1 < (shiftLuma-1), if shiftLuma is not equal to 0, then addDiff takes 0), so that the pseudo code of the above-mentioned way one can be expressed as:

A＝maxY-minY；

shiftLuma＝(A＝＝0)？0:Floor(Log2(Abs(A)))-DIFF_BIT_DEPTH；

shiftLuma＝Max(0,shiftLuma)；

addDiff＝(shiftLuma)？1＜＜(shiftLuma-1):0；

diff＝(A+addDiff)>>shiftLuma；

k＝N+shiftLuma；

Ifdiffis greater than 0,the following applies:

other, the following

a＝0

b＝minC-((a*minY)＞＞k)

In the second embodiment, a may be modified, that is, add an addDiff to a, where (shiftLuma)? 1 < (shiftLuma-1):0 (if shiftLuma is not equal to 0, then addDiff takes 1 < (shiftLuma-1), if shiftLuma is not equal to 0, then addDiff takes 0), so that the pseudo code of the above-mentioned way one can be expressed as:

A＝maxY-minY

shiftLuma ═ (a ═ 0)? Floor (Log2(abs (A))) -DIFF _ BIT _ DEPTH (first predetermined BIT DEPTH)

shiftLuma＝Max(0,shiftLuma)

addDiff＝(shiftLuma)？1＜＜(shiftLuma-1):0

diff＝(A+addDiff)>>shiftLuma

k＝N+shiftLuma

Ifdiffis greater than 0,the following applies:

Other, the following

a＝0

b＝minC-((a*minY)＞＞k)

The third method comprises the following steps: determining an initial scaling coefficient in the intra-frame prediction model parameter corresponding to the target chroma block according to the first chroma value, the second chroma value, the preset value and the second difference value;

and if the fourth difference between the number of the effective bits of the initial scaling coefficient and the second preset bit-depth is greater than 0, performing right shift processing on the initial scaling coefficient according to the fourth difference to obtain the scaling coefficient in the intra-frame prediction model parameter corresponding to the target chroma block. b minC- ((a minY) > k), wherein b is a shift factor, a is a scaling coefficient, minC is a second chromaticity value, minY is a minimum brightness value, and k is a target value.

Wherein, the second preset bit-depth is the bit-depth preset corresponding to the scaling factor, and is stored in the above mentioned device, for example, it can be less than 26 bits, and can be 16 bits, 10 bits, 8 bits, etc.

In an implementation, the first chrominance value, the second chrominance value, the preset value, and the second difference value may be used to determine an initial scaling factor in the intra prediction model parameter corresponding to the target chrominance block, which may be referred to in the first or second manner. Then, a second preset bit-depth preset corresponding to the scaling coefficient can be obtained, then, a fourth difference value between the number of the significant bits of the initial scaling coefficient and the second preset bit-depth is determined, whether the fourth difference value is greater than 0 or not is judged, if the fourth difference value is greater than 0, right shift processing can be performed on the initial scaling coefficient according to the fourth difference value, and the scaling coefficient corresponding to the target chrominance block is obtained. For example, the fourth difference is 4, and the initial scaling factor may be shifted right by 3 bits.

After the scaling factor is determined, a target scaling factor may be determined, and the determination method is the same as the processing in the first method or the second method, which is not described herein again.

Optionally, the right shift processing in the third mode may be:

and shifting the initial scaling coefficient by the fourth difference bit to the right to obtain the scaling coefficient in the intra-frame prediction model parameter corresponding to the target chroma block.

In an implementation, after determining that the fourth difference is greater than 0, the initial scaling factor may be shifted to the right by the fourth difference bit to obtain a scaling factor in the intra prediction model parameter corresponding to the target chroma block.

Optionally, based on the shift processing of the scaling factor, the target value of the normalized shift parameter may also be adjusted, and the corresponding processing may be as follows:

and if the fourth difference is larger than 0, determining the sum of the preset value of the normalized shift parameter and the third difference and the difference of the fourth difference as the target value of the normalized shift parameter.

In an implementation, in case that the third difference is larger than 0 and a fourth difference between the number of significant bits of the initial scaling factor and the second preset bit-depth is larger than 0, a difference between a sum of the preset value of the normalized shift parameter and the third difference and the fourth difference may be determined, and then the difference may be determined as the target value of the normalized shift parameter.

In the third embodiment, after obtaining the target value of the normalized shift parameter, the offset factor may be determined by: a preset offset factor calculation formula may be obtained, that is, b is minC- ((a minY) > k), which represents that a value obtained after minC and a minY are shifted to the right by k bits is differentiated to obtain an offset factor b corresponding to the target chrominance block, and the scaling coefficient a, the second chrominance minC, the target value k of the normalized shift parameter, and the minimum luminance value minY may be substituted into the formula to determine an offset factor b corresponding to the target chrominance block, where k is N + shiftLuma-shiftA, shiftLuma is the third difference mentioned above, N is the preset value of the normalized shift parameter mentioned above, and shiftA is a fourth difference.

In the third embodiment, since the offset factor is obtained based on the scaling factor and the target value of the normalized shift parameter, the offset factor is also changed, that is, the offset factor b may be obtained by recalculating the offset factor using the formula b minC- ((a minY) > k), where minC represents the second chromaticity value, a is the scaling factor, minY is the minimum luminance value, and k is the target value of the normalized shift parameter (i.e., the fourth numerical value).

It should be further noted that, the process is equivalent to further adjustment on the basis of determining the scaling factor and the offset factor, and since the bit-depth of the scaling factor is reduced after the initial scaling factor is shifted to obtain the scaling factor, the complexity of multiplication in the subsequent determination of the prediction information can be reduced.

In addition, if the fourth difference is not greater than 0, the shift processing is not performed on the initial scaling coefficient, i.e., the scaling coefficient is the same as the initial scaling coefficient, and the initial offset factor is the same as the offset factor.

If the initial scaling factor is obtained based on the first mode, the third mode process using pseudo code can be expressed as:

If diff is larger than 0, the following is

Wherein the content of the first and second substances,

shiftA ═ 0? Floor (Log2(Abs (a))) -a _ BIT _ DEPTH (representing that the fourth difference (denoted shiftA) is taken as 0 if a equals 0, or Floor (Log2(Abs (a)) -a _ BIT _ DEPTH if a equals 0, Abs () representing the absolute value, a _ BIT _ DEPTH being the second predetermined BIT-DEPTH) if a equals 0;

shiftA ═ Max (0, shiftA) (meaning that the fourth difference shiftA takes the maximum of 0 and shiftA);

a > > shiftA (meaning that a is right-shifted by a fourth difference bit, resulting in a scaling factor);

k ═ N + shiftLuma-shiftA (a target value k representing the normalized shift parameter is equal to the difference between the sum of the preset value N of the normalized shift parameter and the third difference and the fourth difference);

other, the following

a＝0

b＝minC-((a*minY)＞＞k)

In addition, the scaling factor may be modified, that is, an addA is added to the initial scaling factor, and then (a + addA) is right-shifted by shiftA, which is determined as the final scaling factor, and is (shiftA)? 1 < (shiftA-1) > 0(addA takes the value of 1 < (shiftA-1) if shiftA is not equal to 0, and 0 if shiftA is not equal to 0, so that the pseudo code for performing the shift processing after obtaining the initial scaling factor in the above manner is:

A＝maxY-minY

shiftLuma＝(A＝＝0)？0:Floor(Log2(Abs(A)))-DIFF_BIT_DEPTH

shiftLuma＝Max(0,shiftLuma)

diff＝A>>shiftLuma

k＝N+shiftLuma

Ifdiffis greater than 0,the following applies:

wherein the content of the first and second substances,

shiftA＝(a＝＝0)？0:Floor(Log2(Abs(a)))-A_BIT_DEPTH

shiftA＝Max(0,shiftA)

addA＝shiftA1<<(shiftA-1):0

a＝(a+addA)>>shiftA

k＝N+shiftLuma–shiftA

b＝minC-((a*minY)＞＞k)

Otherwise,the following applies:

a＝0

b＝minC-((a*minY)＞＞k)

in this way, since a is corrected, the prediction information acquired later is more accurate.

If the initial scaling factor is obtained based on the second mode, the pseudo code used in the third mode process can be expressed as:

A＝maxY-minY

shiftLuma＝(A＝＝0)？0:Floor(Log2(Abs(A)))-DIFF_BIT_DEPTH

shiftLuma＝Max(0,shiftLuma)

diff＝A>>shiftLuma

k＝N+shiftLuma

Ifdiffis greater than 0,the following applies:

shiftA＝(a＝＝0)？0:Floor(Log2(Abs(a)))-A_BIT_DEPTH

shiftA＝Max(0,shiftA)

a＝a>>shiftA

k＝N+shiftLuma–shiftA

b＝minC-((a*minY)＞＞k)

Otherwise,the following applies:

a＝0

b＝minC-((a*minY)＞＞k)

in addition, the scaling factor may be modified, that is, an addA is added to the initial scaling factor, and then (a + addA) is right-shifted by shiftA, which is determined as the final scaling factor, and is (shiftA)? 1 < (shiftA-1) > 0(addA takes the value of 1 < (shiftA-1) if shiftA is not equal to 0, and 0 if shiftA is not equal to 0, so that the pseudo code subjected to the shift processing after the initial scaling factor is obtained in the second mode is as follows:

A＝maxY-minY

shiftLuma＝(A＝＝0)？0:Floor(Log2(Abs(A)))-DIFF_BIT_DEPTH

shiftLuma＝Max(0,shiftLuma)

diff＝A>>shiftLuma

k＝N+shiftLuma

Ifdiff is greater than 0,the following applies:

shiftA＝(a＝＝0)？0:Floor(Log2(Abs(a)))-A_BIT_DEPTH

shiftA＝Max(0,shiftA)

addA＝shiftA1<<(shiftA-1):0

a＝(a+addA)>>shiftA

k＝N+shiftLuma–shiftA

b＝minC-((a*minY)＞＞k)

Otherwise,the following applies:

a＝0

b＝minC-((a*minY)＞＞k)

Optionally, the second preset bit-depth is a bit-depth of the intra interpolation filter coefficient.

In an implementation, setting the second preset bit-depth as the bit-depth of the intra interpolation filter coefficients may be aligned with the complexity of intra prediction. For example, in the existing standard, the bit-depth of the intra interpolation filter coefficient is 6 bits, and the second preset bit-depth may also be 6 bits.

Optionally, in this embodiment of the application, when the first difference is not greater than 0, the method for determining the scaling factor and the offset factor may be as follows:

if the first difference is not greater than 0, determining the scaling factor in the intra prediction model parameter to be 0, and determining the offset factor in the intra prediction model parameter to be a second chrominance value.

In an implementation, if the first difference is not greater than 0, it may be determined that the scaling factor is 0, and then b minC- ((a minY) > k) is obtained by using the formula b minC, the target value of the normalized shift parameter, and the minimum luminance value, and then b minC is obtained by substituting the formula b minC, that is, the shift factor is the second chrominance value.

The above method embodiments and the specific implementation thereof may be performed by the above apparatus or system of fig. 1 to 5.

In the embodiment of the present application, when determining the prediction information of the target chrominance block, a maximum luminance value and a minimum luminance value of luminance pixels corresponding to pixels adjacent to the target chrominance block may be obtained, a first chrominance value corresponding to the maximum luminance value and a second chrominance value corresponding to the minimum luminance value are obtained, and then a first difference between the maximum luminance value and the minimum luminance value is determined. If the first difference is greater than 0, right shift processing can be performed on the first difference according to the number of valid bits of the first difference and a first preset bit-depth to obtain a second difference. And then determining intra-frame prediction model parameters corresponding to the target chroma block according to the first chroma value, the second chroma value and the second difference value, and then determining prediction information of the target chroma block according to the intra-frame prediction model parameters and the brightness reconstruction information corresponding to the target chroma block. In this way, when the intra-frame prediction model parameter is determined, the right shift processing is performed on the first difference value between the maximum brightness value and the minimum brightness value according to the number of significant bits of the first difference value and the first preset bit-depth, so that the calculation amount of the intra-frame prediction model parameter can be reduced, and the prediction efficiency of the chroma block can be improved.

The intra prediction model parameters include a scaling factor and an offset factor. Specifically, when the scaling factor is determined, right shift processing is performed on the first difference between the maximum luminance value and the minimum luminance value according to the number of significant bits of the first difference and the first preset bit-depth, so that the calculation amount for determining the scaling factor can be reduced, the calculation amount for determining the offset factor can be further reduced, the complexity for determining the prediction information can be further reduced, and the prediction efficiency of the chrominance block can be improved.

Fig. 13 is a block diagram of a prediction apparatus for a chroma block according to an embodiment of the present application. The apparatus may be implemented as part or all of an apparatus in software, hardware, or a combination of both. The apparatus provided in the embodiment of the present application can implement the processes described in fig. 11 and fig. 12 in the embodiment of the present application, and the apparatus includes: an acquisition module 1310 and a determination module 1320, wherein:

an obtaining module 1310, configured to obtain a maximum luminance value and a minimum luminance value in luminance pixels corresponding to pixels adjacent to a target chrominance block, and obtain a first chrominance value corresponding to the maximum luminance value and a second chrominance value corresponding to the minimum luminance value, which may be specifically used to implement the obtaining functions and implicit steps of fig. 11 and 12;

a determination module 1320 for:

if the first difference value between the maximum brightness value and the minimum brightness value is larger than 0, performing right shift processing on the first difference value according to the number of effective bits of the first difference value and a first preset bit depth bit-depth to obtain a second difference value;

determining intra-frame prediction model parameters corresponding to the target chroma block according to the first chroma value, the second chroma value and the second difference value;

the prediction information of the target chroma block is determined according to the intra prediction model parameter and the luminance reconstruction information corresponding to the target chroma block, and may be specifically used to implement the determining function of fig. 11 and fig. 12 and the implicit steps included in the determining function.

Optionally, the determining module 1320 is configured to:

determining a third difference value between the number of significant bits of the first difference value and the first preset bit-depth;

and if the third difference is larger than 0, performing right shift processing on the first difference according to the third difference to obtain a second difference.

Optionally, the determining module 1320 is configured to:

and shifting the first difference value to the right by the third difference value to obtain the second difference value.

Optionally, the determining module 1320 is configured to:

and determining intra-frame prediction model parameters corresponding to the target chrominance block according to the first chrominance value, the second chrominance value, the preset value of the normalized shift parameter, the second difference value and the minimum luminance value.

Optionally, the determining module 1320 is configured to:

determining a scaling coefficient in an intra-frame prediction model parameter corresponding to the target chroma block according to the first chroma value, the second difference value and the preset value;

and determining an offset factor in an intra-frame prediction model parameter corresponding to the target chroma block according to the scaling coefficient, the second chroma value, a target value of a normalized shift parameter and the minimum brightness value, wherein the target value of the normalized shift parameter is determined according to the preset value of the normalized shift parameter and the third difference value.

Optionally, the determining module 1320 is configured to:

The determining module 1320, configured to:

wherein the content of the first and second substances,

Optionally, the determining module 1320 is configured to:

determining an initial scaling coefficient in an intra-frame prediction model parameter corresponding to the target chroma block according to the first chroma value, the second chroma value, the preset value and the second difference value;

and if the fourth difference between the number of the effective bits of the initial scaling coefficient and the second preset bit-depth is greater than 0, performing right shift processing on the initial scaling coefficient according to the fourth difference to obtain the scaling coefficient in the intra-frame prediction model parameter corresponding to the target chroma block.

Optionally, the determining module 1320 is configured to:

and shifting the initial scaling coefficient to the right by the fourth difference bit to obtain the scaling coefficient in the intra-frame prediction model parameter corresponding to the target chroma block.

Optionally, the determining module 1320 is further configured to:

and if the fourth difference is larger than 0, determining the difference between the sum of the preset value of the normalized shift parameter and the third difference and the fourth difference as the target value of the normalized shift parameter.

Optionally, the determining, according to the scaling coefficient, the second chrominance value, the target value, and the minimum luminance value, an offset factor in an intra prediction model parameter corresponding to the target chrominance block includes:

It should be noted that: in the prediction apparatus for a chroma block according to the above embodiment, when determining prediction information of a chroma block, only the division of the functional modules is illustrated, and in practical applications, the function distribution may be completed by different functional modules according to needs, that is, the internal structure of the apparatus may be divided into different functional modules to complete all or part of the functions described above. In addition, the prediction apparatus for a chroma block and the method embodiment for predicting a chroma block provided in the above embodiments belong to the same concept, and specific implementation processes thereof are described in the method embodiment and are not described herein again.

The present application also provides a computer-readable storage medium storing instructions that, when executed on a computing device, cause the computing device to perform the above-described prediction method for a chroma block.

The present application also provides a computer program product comprising instructions which, when run on a computing device, cause the computing device to perform the above-described method of prediction of a chroma block.

In the above embodiments, all or part of the implementation may be realized by software, hardware, firmware or any combination thereof, and when the implementation is realized by software, all or part of the implementation may be realized in the form of a computer program product. The computer program product comprises one or more computer program instructions which, when loaded and executed on a server or terminal, cause the processes or functions described in accordance with embodiments of the application to be performed, in whole or in part. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wire (e.g., coaxial cable, fiber optics, digital subscriber line) or wirelessly (e.g., infrared, wireless, microwave, etc.). The computer readable storage medium can be any available medium that can be accessed by a server or a terminal or a data storage device, such as a server, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (such as a floppy Disk, a hard Disk, a magnetic tape, etc.), an optical medium (such as a Digital Video Disk (DVD), etc.), or a semiconductor medium (such as a solid state Disk, etc.).

The above description is only one embodiment of the present application and should not be taken as limiting the present application, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for predicting a chroma block, the method comprising:

obtaining a maximum luminance value and a minimum luminance value based on luminance pixels corresponding to neighboring pixels of the target chrominance block,

obtaining a first chrominance value and a second chrominance value, wherein the first chrominance value is related to the maximum luminance value, and the second chrominance value is related to the minimum luminance value;

if the first difference value between the maximum brightness value and the minimum brightness value is larger than 0, carrying out shift operation on the first difference value according to the number of effective bits of the first difference value and a first preset bit depth bit-depth to obtain a second difference value;

determining a cross-component linear mode CCLM parameter corresponding to the target chroma block according to the first chroma value, the second chroma value and the second difference value;

and determining a predicted value of the target chroma block according to the CCLM parameter and the brightness reconstruction information corresponding to the target chroma block.

2. The method of claim 1, wherein the number of significant bits of the second difference is equal to the first predetermined bit depth, bit-depth.

3. The method of claim 1, wherein determining the CCLM parameter corresponding to the target chroma block according to the first chroma value, the second chroma value and the second difference value comprises:

and determining a CCLM parameter corresponding to the target chrominance block according to the first chrominance value, the second difference value and the minimum luminance value.

4. The method of claim 3, wherein determining the CCLM parameter corresponding to the target chroma block according to the first chroma value, the second difference value and the minimum luma value comprises:

determining a scaling coefficient in a CCLM parameter corresponding to the target chroma block according to the first chroma value, the second chroma value and the second difference value;

and determining a shift factor in the CCLM parameter corresponding to the target chrominance block according to the scaling coefficient, the second chrominance value and the minimum luminance value.

5. The method of claim 4, wherein determining the offset factor in the CCLM parameter corresponding to the target chroma block according to the scaling factor, the second chroma value and the minimum luma value comprises:

b ═ min C- ((a × min Y) > k), where b is the offset factor, a is the scaling factor, min C is the second chrominance value, min Y is the minimum luminance value, and k is a target value.

6. The method of any of claims 1 to 5, further comprising:

and if the first difference value is not greater than 0, determining that the scaling coefficient in the CCLM parameter is 0, and determining that the offset factor in the CCLM parameter is the second chrominance value.

7. A method as claimed in any one of claims 1 to 5, wherein the first predetermined bit-depth is less than the bit-depth of the luminance pixel.

8. The method of any of claims 1 to 5, wherein shifting the first difference value further comprises: preprocessing the first difference value;

shifting the first difference value comprises: right shifting the preprocessed first difference to reduce a number of significant bits of the first difference.

9. The method of any of claims 1 to 5, wherein shifting the first difference value comprises: right shifting the first difference to reduce a number of valid bits of the first difference.

10. The method according to any one of claims 1 to 5, wherein the luma block corresponding to the target chroma block is a downsampled luma block.

11. An apparatus for predicting a chroma block, the apparatus comprising:

the acquisition module is used for acquiring a maximum brightness value and a minimum brightness value based on brightness pixels corresponding to adjacent pixels of a target chromaticity block, and is also used for acquiring a first chromaticity value and a second chromaticity value, wherein the first chromaticity value is related to the maximum brightness value, and the second chromaticity value is related to the minimum brightness value;

a determination module to:

12. The apparatus of claim 11, wherein the number of significant bits of the second difference is equal to the first predetermined bit depth, bit-depth.

13. The apparatus of claim 11, the determination module to:

14. The apparatus of claim 13, wherein the determining module is configured to:

15. The apparatus of claim 14, wherein the determining module is configured to determine a shift factor in a CCLM parameter corresponding to the target chroma block according to the scaling factor, the second chroma value and the minimum luma value, and comprises:

b ═ min C- ((a × min Y) > k), where b is the offset factor, a is the scaling factor, min C is the second chrominance value, minY is the minimum luminance value, and k is a target value.

16. The apparatus according to any one of claims 11 to 15, wherein the determining module is further configured to:

17. Apparatus according to any of claims 11 to 15, wherein said first predetermined bit-depth is less than the bit-depth of a luminance pixel.

18. The apparatus according to any one of claims 11 to 15, wherein the determining module is further configured to:

preprocessing the first difference value;

shifting the first difference value comprises: and carrying out right shift operation on the preprocessed first difference value.

19. The apparatus according to any one of claims 11 to 15, wherein the determining module is specifically configured to:

right shifting the first difference to reduce a number of valid bits of the first difference.

20. The apparatus according to any one of claims 11 to 15, wherein the luma block corresponding to the target chroma block is a downsampled luma block.

21. An apparatus for prediction of a chroma block, the apparatus comprising a memory and a processor, wherein the memory is configured to store processor-executable instructions;

the processor configured to perform the prediction method of the chroma block of any one of claims 1 to 10.

22. A computer-readable storage medium storing instructions that, when executed on a computing device, cause the computing device to perform the method of predicting a chroma block according to any one of claims 1 to 10.